^  / 

J/ 


'Ji 


PRACTICAL  TREATISE 


ON   THE 


CONSTRUCTION,  HEATING,  AND  VENTILATION 


HOT-HOUSES; 


INCLUDING 


CONSERVATORIES,  GREEN-HOUSES,  GRAPERIES, 


AND  OTHER  KINDS  OF 


HORTICULTURAL  STRUCTURES. 


WITH  PRACTICAL  DIRECTIONS  FOR  THEIR  MANAGEMENT,  IN 
REGARD  TO  LIGHT,  HEAT,  AND  AIR. 


ILLUSTRATED   WITH    NUMEROUS    ENGRAVINGS. 


BY  ROBERT  B.  LEUCHARS, 

GARDEN   ARCHITECT. 


BOSTON: 
JOHN    P.    JEWETT    AND    COMPANY, 

17  &  19  Cornhill. 

1851. 


L5 


UHSKARY-AGWICUL.TIJWE 


Entered  according  to  Act  of  Congress,  in  the  year  1850, 

BY  JOHN  P.  JEWETT  &  Co., 
In  the  Clerk'a  Office  of  the  District  Court  of  the  District  of  Massachusetta, 


Stereotyped  by 
HOBART    &    ROBBINS; 

NEW  ENGLAND  TYPE  AND   STEREOTYPE  FOUNDERY. 
BOSTON. 


TO 


STreatfse, 

DESIGNED  TO  PROMOTE  THE  ADVANCEMENT  OF  EXOTIC  HORTICULTURE. 
OP  WHICH    HE  IS  A  ZEALOUS    PATBON  AND   ADMIRES, 

I*  M^pectMIg  Drticatefc, 

BI    HIS    OBLIGED    AND    OBEDIENT    SKBTAHT, 

THE    AUTHOK. 


66T791 


0&    is    K  Oi     -OiJlV? 

PEEFACE. 


HAVING  for  many  years  past  devoted  my  attention 
to  the  subjects  treated  of  in  this  work,  and  from  the 
general  call  for  appliable  information  thereon,  I  have 
been  induced  to  give  it  to  the  public,  in  the  full 
persuasion  that  it  will  be  acceptable  to  horticultur- 
ists, gardeners,  and  others  engaged  in  this  depart- 
ment of  horticulture.  From  the  numerous  inquiries 
which  I  have  received,  there  appears  to  be  a  great 
want  of  practical  knowledge  on  these  subjects  ;  and 
though  much  information  may  be  gleaned  from  vari- 
ous English  works,  they  are  either  unobtainable,  or 
the  information  is  inapplicable  to  the  wants  of  this 
country. 

When  I  commenced  this  treatise,  I  intended  it  as 
a  series  of  articles  for  periodical  publication ;  but 
the  development  of  the  subjects,  and  the  accumula- 
tion of  facts,  swelled  it  to  such  a  size  as  to  render 
its  publication  in  that  form  impossible.  In  prepar- 
ing it  for  the  press,  in  its  present  form,  I  have  been 
desirous  to  add  nothing  but  what  is  necessary  to  a 
full  understanding  of  the  subject  in  hand,  and  have 
given  figures  and  diagrams  where  illustration  is 
required. 

The  changes  which  have  occurred,  during  the  last- 
twenty  years,  in  the  method  of  constructing  and 


PREFACE. 


managing  horticultural  structures,  render  the  works 
of  that  period  of  little  value  to  gardeners  at  the 
present  day.  I  have  here  given  all  the  latest  im- 
provements and  most  approved  methods  at  present 
in  use,  with  plans  and  suggestions  for  their  further 
improvement. 

From  what  has  been  said,  I  hope  no  one  will  sup- 
pose that  this  treatise  is  given  as  a  complete  work 
on  Exotic  Horticulture.  Much  has  yet  to  be  learned, 
on  many  points  connected  with  hot-houses,  which 
futurity  will,  no  doubt,  unfold. 

My  warmest  expressions  of  thanks  are  due  to 
Professor  Dana,  of  Yale  College,  for  the  generous 
manner  in  which  he  has  favored  me  with  his  opinions. 
The  readiness  with  which  that  gentleman  has  replied 
to  my  inquiries,  on  matters  of  science  relating  to 
my  subject,  even  in  the  midst  of  his  laborious  literary 
pursuits,  shows  how  willing  he  is  to  aid  the  most 
humble  inquirer.  This  expression  of  thanks  is  due 
from  me  here,  as  the  only  way  in  which  I  can  suf- 
ficiently show  the  high  value  at  which  I  estimate 
his  kindness  and  liberality. 

K.  B.  L. 

Boston,  Oct.  3,  1850. 


INTRODUCTION. 


THE  object  of  the  following  treatise  is  chiefly  to  lay  before 
its  readers  a  series  of  facts  and  observations  relating  to  the  con- 
struction and  general  management  of  all  kinds  of  horticultural 
structures,  drawn  from  the  developments  of  science,  and  an 
extended  experience,  with  the  view  of  leading  those  who  are 
interested  in  this  delightful  pursuit  to  a  more  practical  inquiry 
regarding  the  comparative  cost  and  economy  of  the  various 
methods  now  commonly  adopted,  as  well  as  to  draw  the  atten- 
tion of  practical  gardeners  to  the  utility  of  studying  the  theory 
as  well  as  the  practice  of  those  manifold  operations  on  which  the 
success  of  exotic  horticulture  depends. 

In  a  short  treatise,  on  such  comprehensive  and  varied  subjects, 
it  is  impossible  to  be  strictly  scientific ;  but  we  have  endeavored 
to  show  the  rationale  of  those  methods  and  operations  which  we 
have  here  recommended,  and  which  have  been  successfully  car- 
ried out  by  us  in  practice.  The  treatise  is  avowedly  a  practical 
one,  and  intended  chiefly  for  the  use  of  practical  gardeners,  and 
those  desirous  of  obtaining  that  knowledge  which  is  necessary  to 
enable  them  to  superintend  the  erection  and  future  management 
of  their  own  garden  structures.  In  the  management  of  hot- 
houses, there  is  a  systematic  regularity  required  in  all  the  oper- 
ations, a  neglect  of  which  is  generally  attended  with  disorder 
and  confusion.  In  fact,  there  is  a  system,  the  details  of  which 
succeed  each  other  like  the  links  of  a  chain,  each  operation  being 
essentially  connected  with  the  one  immediately  following  and 
preceding  it ;  and  here  we  have  a  most  encouraging  truth,  that 
the  more  scientific  our  principles  of  working,  the  more  simple 
and  easily  performed  are  our  operations,  and  the  more  reliable 
are  the  results. 


8  INTRODUCTION. 

It  is  doubtful  if  any  branch  of  horticulture  has  received  less 
aid  from  science  than  that  which  forms  the  subject  of  the  present 
work.  Science  has  indeed  been  brought  to  bear  upon  horticul- 
tural generalities,  but,  as  far  as  regards  its  application  to  exotic 
jiorticultu,ral  .details,  it  is  little  better  than  a  sealed  book ;  and 
hence  it  is  that  w,e', find  cultivators  clinging  to  antiquated  sys- 
tems, which  the  plain  demonstrations  of  science  and  practice  are 
Jarly  f)i?ovin£'te<fee'  tibsutd.  Amateurs,  who  adopt  exotic  horti- 
culture as  an  amusement,  and  pursue  it  with  enthusiasm,  are 
very  apt  to  be  misled  by  the  advice  of  those  who  are  more  igno- 
rant than  themselves.  They  are  easily  led  into  extremes  ;  and 
nothing  is  more  common  than  for  such  persons,  in  their  zeal, 
to  adopt  one  error,  under  the  plausible  pretext  of  avoiding 
another. 

From  the  importance  of  LIGHT,  HEAT,  and  Am,  in  the  econo- 
my of  vegetable  life,  it  is  obvious  why  an  architect  is  profession- 
ally incapable  of  constructing  a  house  for  the  growth  of  plants 
or  exotic  fruits,  without  possessing  a  knowledge  of  the  require- 
ments and  functions  to  be  performed  by  the  silent  inhabitants ; 
and  hence  it  is,  that,  by  studying  these  principles  in  connection 
with  other  branches  of  science,  we  arrive  at  the  end  more  rapidly 
and  successfully.  In  other  words,  cultivation  becomes  more  cer- 
tain as  it  becomes  more  scientific.  Practical  illustrations  will 
hereafter  be  given,  to  show  that  horticultural  structures,  instead 
of  being  subordinate  to  architectural  arrangements,  as  they  gen- 
erally are,  must  be  accommodated  to  the  necessities  and  require- 
ments of  vegetable  life,  before  satisfaction  can  be  afforded  to  the 
possessor,  or  cultivation  carried  on  in  perfection. 

If  we  take  a  glance  at  the  progress  of  horticulture  in  Europe 
during  the  last  twenty  years,  we  cannot  fail  to  perceive  that  its 
advancement  has  been  parallel  with  the  developments  of  chemi- 
cal and  physiological  science.  Almost  every  succeeding  year 
has  brought  with  it  some  new  and  important  improvement  in 
practice,  and  thrown  additional  light  upon  some  hitherto  disputed 
question.  Although  gardening  has,  in  some  solitary  instances, 
been  remaining  stationary,  the  cause  is  by  no  means  obscure. 
Gardening  is  encouraged  just  in  proportion  to  the  satisfaction 
it  affords.  It  gives  satisfaction  according  to  its  success,  and 


INTRODUCTION. 


success  is  in  proportion  to  the  amount  of  practical  experience 
founded  upon  a  scientific  basis. 

Whatever  causes  exist  to  prevent  the  operations  of  gardening 
from  being  carried  out  on  scientific  principles,  it  is  nevertheless 
true,  that  no  methods  can  be  generally  applicable,  or  universal 
in  their  results,  that  have  not  such  principles  for  their  bases.  To 
be  guided  by  them,  it  is  not  necessary  that  the  gardener  should 
be  a  mere  reader  of  books,  a  studier  of  theories,  or  a  continual 
performer  of  experiments ;  he  must  add  to  the  precepts  of  others 
the  acquisitions  of  his  own  experience,  and  aim  constantly  at 
progress,  by  learning  practically  the  principles  upon  which  his 
operations  rest  for  their  success.  It  is  not  the  lot  of  every  one 
to  discover  truths  hitherto  unknown,  but  almost  every  one  en- 
gaged in  the  practice  of  horticulture  can  do  something  towards 
improvement,  by  enforcing  those  already  known  by  stronger 
evidence,  facilitating  them  by  a  clearer  method,  and  elucidating 
them  by  brighter  illustrations. 

There  is  a  wide-spread  antipathy  to  all  kinds  of  book  instruc- 
tion, and  book  gardening  is  ridiculed  by  many  who  call  them- 
selves gardeners.  It  is,  nevertheless,  a  well  ascertained  fact, 
that  those  who  rail  at  book  practice  are  not  only  the  worst  prac- 
ticals,  but  also  the  worst  theorists,  and  the  worst  reasoners  upon 
matters  of  practical  import.  Indeed,  there  are  few  who  are  more 
slow  to  recognize  the  benefits  of  the  valuable  knowledge  to  be 
found  in  the  works  of  the  eminent  horticulturists  of  this  country, 
than  those  by  whom  it  is  most  required. 

Notwithstanding  the  valuable  works  which  have  lately  been 
given  to  the  world,  on  horticulture  and  the  kindred  arts,  by 
eminent  writers,  little  or  nothing  has  been  done  in  the  depart- 
ment embraced  by  this  treatise.  Horticultural  structures  of  all 
kinds  continue  to  be  made,  and  managed,  with  the  same  disre- 
gard to  the  actual  habits  and  requirements  of  plants,  as  they 
were  a  century  ago.  And,  though  some  structures  of  this  kind 
have  been  constructed  upon  plans  and  principles  in  accordance 
with  modern  knowledge,  yet  these  are  a  very  small  exception. 
Many  apparently  fine  structures  could  be  pointed  to,  which  are 
rendered  comparatively  useless  for  the  purposes  for  which  they 


10  INTRODUCTION. 

were  built,  on  account  of  a  deficiency  of  knowledge  on  the  part 
of  those  who  superintended  their  erection. 

It  is  a  common  error  for  gardeners,  and  others,  who  erect 
glazed  structures,  to  suppose  that  the  kind  of  house  perfectly 
suitable  in  one  place  will  be  equally  so  in  another ;  or  that  the 
same  arrangement  answerable  for  one  purpose  will  answer 
equally  well  for  all  purposes  to  which  a  glazed  structure  may 
be  applied.  Some  of  the  consequences  of  these  errors  will  be 
more  particularly  specified  in  a  subsequent  part  of  this  work ;  as 
also  the  external  forms  and  internal  arrangements  which  we 
have  found  most  suitable  to  the  different  purposes.  The  influ- 
ence which  a  servile  adherence  to  old  methods  has  upon  the 
progress  of  horticulture,  is  chiefly  manifest  to  those  who  are 
most  liable  to  be  censured  for  innovations.  Yet  it  is  doubtful 
whether  the  odium  incurred  is  not  more  than  compensated  by 
the  pleasure  which  arises  from  the  rewards  of  perseverance,  by 
which  we  are  enabled  to  abandon  bad  systems,  as  we  gain  more 
confidence  in  those  that  are  better. 

It  is  said  that  practice  is  the  best  of  all  teachers ;  that  as  our 
practice  is  lengthened,  our  experience  is  increased.  However 
this  axiom  may  hold  good  in  the  common  affairs  of  life,  it  is 
frequently  reversed  among  practical  men,  and  years  pass  away 
without  any  enlargement  of  knowledge,  or  rectification  of 
judgment.  There  are,  indeed,  many  who  never  endeavor  to 
improve,  notwithstanding  the  opportunities  which  may  be 
afforded  them.  The  opinions  they  have  received,  and  the 
practice  they  have  learned,  are  seldom  recalled  for  examination, 
and,  having  once  supposed  them  to  be  right,  they  can  never 
discover  them  to  be  erroneous.  From  this  preconceived  acqui- 
escence, few  are  entirely  free ;  from  a  dislike  to  apparently  super- 
fluous labor,  and  from  a  fear  of  uncertain  results,  many  stand 
still  when  they  might  go  forward. 

Some  may  say,  that  if  a  practical  man  performs  the  operations 
which  others  have  taught  him,  and  succeeds  as  well  as  others 
have  done,  he  does  all  that  can  be  expected  from  him.  But  this 
is  doing  nothing  for  improvement,  and  very  little  for  himself. 
It  is  every  man's  duty  to  endeavor  to  excel,  both  on  account 
of  his  profession  and  of  himself,  as  well  as  those  who  employ 


INTRODUCTION.  1 1 

him.  It  is  easy  to  perceive  that  a  gardener  must  not  only  know 
how  to  do,  but  have  his  reasons  for  doing.  A  man  who  continues 
to  do  his  annual  operations  by  mere  routine,  without  knowing  the 
foundation  or  reasons,  cannot  deviate  from  the  narrow  path  in 
which  he  is  confined,  when  any  unexpected  accident  occurs. 

In  the  following  treatise,  we  have  endeavored  to  explain  these 
principles,  as  far  as  they  have  been  connected  with  the  subjects 
upon  which  it  treats,  and  to  illustrate  them  in  such  a  manner  as 
to  be  easily  understood  by  the  general  reader. 

The  first  part  of  the  work  we  have  devoted  to  the  construction 
of  Conservatories,  Graperies,  Green-houses,  Pits,  Frames,  and 
every  kind  of  horticultural  buildings,  giving  the  different  posi- 
tions and  aspects  most  suitable  to  each,  and  the  various  purposes 
for  which  particular  structures  are  best  adapted.  We  have  also 
fully  considered  the  different  kinds  of  materials  generally  used 
in  the  erection  of  these  buildings,  and  the  respective  merits  of 
each.  Glass,  and  its  influences  on  vegetation,  are  also  fully  con- 
sidered and  discussed  in  this  part,  —  a  subject  which  has  hith- 
erto received  very  little  attention  from  horticultural  writers,  but 
is  nevertheless  one  of  the  most  important  items  connected  with 
exotic  gardening.  We  have  given  the  useful  experiments  of 
Mr.  Hunt,  on  LIGHT,  and  its  effects  on  vegetation  and  germina- 
tion, and  all  other  information  which  we  have  considered  use- 
ful on  this  part  of  our  subject. 

The  second  part  embraces  the  most  approved  methods  of 
heating  horticultural  structures,  giving  the  principles  of  com- 
bustion and  consumption  of  fuel,  the  prevention  of  smoke,  and 
the  various  volatile  products  of  the  coal ;  the  construction  of 
flues  and  furnaces ;  the  different  sizes  and  heating  powers 
of  pipes  and  boilers  ;  the  circulation  of  water,  and  the  pecu- 
liar modifications  of  apparatus  suitable  for  particular  struc- 
tures. We  have  given  a  considerable  number  of  illustrations 
in  this  part,  showing  various  methods  of  heating,  with  all  of 
which  we  have  had  extensive  practice,  and  some  of  them  on 
entirely  new  principles.  The  various  merits  of  hot  air  and 
hot  water  are  considered  on  scientific  as  well  as  on  practical 
grounds,  and  each  acknowledged  for  what  it  is  worth, 

The  third  part  may  be  called  the  theory  and  practice  of 
2 


12  INTRODUCTION. 

ventilation,  including  some  valuable  investigations  of  the  pnys- 
iological  effects  of  the  atmosphere,  under  different  circumstances, 
and  at  different  temperatures.  Many  of  our  remarks  have 
assumed  a  greater  length  than  we  originally  intended,  and  if 
some  appear  repetitionary,  this  is  in  order  to  avoid,  as  much 
as  possible,  all  strictly  scientific  technicalities  and  abstruse 
reasoning,  whereby  the  minds  of  practical  men  are  frequently 
unable  to  understand  fully  the  end  to  which  you  direct  them. 
We  have  added  a  section  on  the  protection  of  horticultural 
structures  in  severe  weather,  —  a  subject  which  is  worthy  of 
much  consideration. 

I  may  observe,  that,  in  pointing  out  and  freely  comment- 
ing on  principles  and  practices  which  are  erroneous,  but  which 
have  been  practised  and  promulgated  by  others,  it  is  under  the 
impression  that  such  errors,  carrying  with  them,  in  general, 
some  plausibility,  have  led,  and  may  still  lead,  others  to  fall  into 
similar  mistakes.  However  invidious,  therefore,  be  the  task  of 
pointing  out  these  errors,  it  would  be  manifestly  impossible  to 
write  on  this  subject  without  noticing  them,  and,  if  possible, 
pointing  out  the  difference  between  right  and  wrong.  This  is  the 
only  apology  which  can  be  offered  for  the  freedom  with  which 
some  of  the  opinions  and  methods  of  others  have  been  com- 
mented on  in  the  various  parts  of  this  treatise.  We  have,  how- 
ever, expatiated  on  them  candidly,  and  in  the  true  spirit  of 
inquiry,  pointing  out  the  applicability  of  their  principles  and  the 
utility  of  their  practice. 

The  different  parts  of  the  subject  have  been  arranged  under 
different  heads,  as  far  as  has  been  practicable,  in  order  that  any 
of  the  different  parts  may  be  pursued  intelligibly  and  clearly. 
In  extenuation  of  any  errors  which  may  be  found,  we  hope  it 
will  be  considered  that  many  of  the  points  treated  on  are 
entirely  new,  and  as  yet  undeveloped ;  that  no  comprehensive 
view  of  the  principles  of  exotic  culture  has  yet  been  given. 
But  we  must  no.t  be  understood  to  offer  excuses  for  any  errors, 
other  than  those  that  are  embraced  by  this  extenuating  clause, 
which  will  be  acknowledged  if  rectified  in  the  true  spirit  of 
philosophical  inquiry. 


PART    I.    CONSTRUCTION    OF 
HOT-HOUSES. 


SECTION    I. 

SITUATION. 

1.  Site  and  position.  —  Before  proceeding  to  details  regard- 
ing the  structures  themselves,  it  will  be  necessary  to  consider, 
briefly,  the  situation  on  which  the  structures  are  to  stand.  A 
glazed  structure  depends  for  its  effect  very  much  upon  its  posi- 
tion; and  as  the  position  most  desirable  for  effect  may  very 
possibly  militate  against  the  utility  and  efficiency  of  the  struc- 
ture, the  question  presents  a  double  claim  to  our  consideration. 
In  illustrating  the  position  most  desirable  for  the  erection  of 
houses  for  horticultural  purposes,  I  assume  that  the  paramount 
object  is  utility.  I  will  subsequently  point  out  reasons  which 
frequently  occur  to  render  the  position  of  green-houses  and  con- 
servatories beyond  the  control  of  the  erector. 

By  site  and  position  I  must  not  be  understood  to  imply  merely 
the  aspect  upon  which  a  house  for  horticultural  purposes  should 
stand.  The  aspect  of  a  house  may  be  affected  by  circumstances 
which  have  no  relation  to  its  site.  In  other  words,  the  glazed 
elevations  of  a  house  may  be  turned  in  any  direction,  while  the 
position  may  be  altogether  unsuitable  whichever  aspect  may  be 
given  to  it.  The  weather,  at  all  seasons  of  the  year,  has  unde- 
niably more  influence  on  a  house  in  some  situations  than  it  has 
upon  houses  in  others  more  favorably  placed ;  and  this  influence 
is  sensibly  felt  by  the  products  which  are  grown  within  them. 


14  SITUATION. 

The  climate,  and  especially  the  prevailing  winds  of  the  locality, 
should  be  studied  attentively,  in  order  to  anticipate  their  changes, 
and  avoid,  as  far  as  possible,  their  injurious  effects.  No  doubt 
it  is  sometimes  difficult  to  ascertain  the  precise  spot  on  which  to 
erect  hot-houses,  with  these  considerations  in  view,  particularly 
when  the  ground  is  extensive  and  the  choice  limited ;  yet,  in 
most  places,  there  are  some  spots  preferable  to  others.  A  bleak, 
elevated  position  should  never  be  chosen,  if  there  be  any  choice 
left.  If  a  bare,  elevated  spot  must  be  chosen,  either  on  account 
of  there  being  no  alternative,  or  from  other  adventitious  consid- 
erations, such  as  to  obtain  a  commanding  view  of  the  surround- 
ing country,  or  to  present  a  more  imposing  appearance  from  the 
mansion,  or  from  any  other  point  of  sight  from  which  it  may  be 
thought  desirable  to  view  them,  then  the  background  should 
always  be  planted  up  with  trees.  This  is  indispensable,  for  two 
important  reasons  :  — 

(1.)  For  shelter.  The  northern  winds  are  cold  and  biting  in 
frosty  weather,  and  air  can  be  admitted  when  the  houses  are 
well  sheltered,  when  it  otherwise  would  be  impossible  to  do  so 
without  injury  to  the  plants.  Moreover,  the  north  side  of  a 
horticultural  structure  of  any  kind  is  the  only  one  that  can  be 
appropriately  sheltered  with  tall  growing  trees.  It  is,  there- 
fore, the  more  necessary  that  trees  should  be  planted  close 
enough  to  break  the  wind,  but  not  so  close  that  their  overhang- 
ing branches,  when  they  have  attained  their  full  size,  may  drip 
upon  the  glass.  This  last  is  an  evil  which  ought,  in  all  cases, 
to  be  avoided.  Neither  ought  new  houses  to  be  placed  so  near 
trees,  already  standing  on  the  grounds,  that  these  circumstances 
may  occur. 

(2.)  For  beauty  and  effect.  I  do  not  mean,  in  this  paragraph, 
to  allude  to  hot-houses  in  general  as  handsome  architectural 
objects  in  the  grounds  of  a  country  residence, — to  which  consider- 
ation I  will  subsequently  allude, — but  merely  to  the  effect  which 
hot-houses  of  the  cheapest  and  plainest  description  may  be  easily 
made  to  produce,  without  much  trouble  or  expense,  or  without 
adding  one  cent  to  the  cost  of  the  structure  itself.  Let  any  per- 
son take  a  glance  at  a  structure  of  glass,  or  range  of  such  struc- 
tures, having  nothing  but  the  distant  sky  for  a  background,  and 


SITUATION. 


compare  it  with  another,  resting  upon  the  green,  glossy  foliage 
of  luxuriant  trees  towering  above  them,  and  these  again  reflect- 
ing their  irregular  outlines  against  the  cloudless  horizon  behind 
them,  and  he  cannot  fail  to  be  struck  with  the  tame  and  spirit- 
less appearance  of  the  former,  and  equally,  also,  by  the  pictur- 
esque and  pleasing  effect  produced  by  the  latter. 

A  conservatory,  or  green-house,  avowedly  ornamental,  and 
intended  as  an  object  of  architectural  beauty,  or  of  individual 
elegance,  requires  the  most  exquisite  taste  and  skill  in  harmo- 
nizing the  objects  around  it.  These  surrounding  objects, 
whether  for  utility  or  embellishment,  may  be  so  arranged  as  to 
heighten  the  effect  of  the  whole,  without  impairing  the  individ- 
ual effect  of  the  structure,  or  hiding  any  of  its  beauties.  The 
various  features  of  the  structure  should  be  presented  to  view 
from  different  points  ;  and  if,  from  any  walk  or  portion  of  the 
grounds,  the  structure  present  rather  an  unfavorable  aspect,  then 
some  object  should  be  interposed  to  obstruct  the  view  from  this 
particular  point.  When  a  walk  is  led  along  the  skirt  of  a  wood 
or  plantation,  where  a  glimmering  of  the  structure  is  continu- 
ously visible  from  among  the  trees,  the  effect  is  bad,  and  ought, 
by  all  means,  to  be  obviated  by  planting  shrubbery  and  under- 
wood, leaving  here  and  there  an  open  vista  through  which  a 
full  view  of  the  whole  building,  or  portion  of  it,  may  be  obtained. 

It  has,  for  some  time,  been  the  rage  in  this  country  to  place 
horticultural  buildings  of  all  kinds  upon  eminences,  and  sur- 
round them,  either  wholly  or  in  front,  with  square  terraces. 
These  terraces  are  made  sometimes  of  brick,  in  all  its  primi- 
tive redness,  sometimes  of  small  stones  and  mortar,  and  more 
frequently,  perhaps,  of  grass,  nearly  perpendicular.  It  is  gen- 
erally difficult  to  discover  which  is  the  most  unnatural  and 
unsightly  ;  arid,  in  nineteen  cases  out  of  twenty,  we  have  found 
the  terrace  itself,  of  whatever  materials,  of  very  questionable 
taste.  Terraces  grew  out  of  necessity,  —  not  out  of  taste,  — 
except,  perhaps,  in  the  Dutch  school,  which  an  able  writer  on 
this  subject  styles  "a  double-distilled  compound  of  labored 
symmetry,  regularity,  and  stiffness."^  A  terrace  may  be  in  very 
good  taste,  in  connection  with  a  pretty  little  Tuscan  or  Italian 

*  Downirig's  Landscape  Gardening. 


16  SITUATION. 

villa,  when  it  is  finished  and  ornamented  as  a  terrace  should 
be,  i.  e.,  with  vases,  urns,  &c.,  of  sizes  and  forms  harmonizing 
properly  with  the  architecture  of  the  building.  The  same  prin- 
ciple may  be  applied  to  detached  conservatories  when  placed  in 
the  grounds  as  ornamental  objects. 

While  speaking  of  terraces,  it  may  not  be  out  of  place  to 
remark,  that,  about  some  of  the  finest  gardens  of  this  country, 
these  grass  walls  are  introduced  to  absolute  satiety.  Nothing 
like  a  gentle,  undulating  surface  is  for  a  moment  tolerated,  but, 
as  a  matter  of  custom,  the  ground  must  be  levelled,  and  flanked 
by  a  terrace.  Now  we  think  that  when  terraces  are  found  neces- 
sary in  front  of  a  garden  structure,  of  an  ornamental  charac- 
ter, they  ought  to  be  of  a  different  character  from  those  intermi- 
nable sod  banks  so  liberally  constructed  about  some  fine  places 
that  we  could  mention,  but  forbear  doing  so,  on  the  principle, 
that,  where  much  has  been  done,  a  few  errors  in  taste  may  be 
justified.  However,  it  cannot  be  denied  that  a  steep  bank  of 
grass,  twelve  or  twenty  feet  deep  and  as  many  from  the  walls 
of  the  building,  void  of  any  architectural  decoration  or  ornament 
of  any  description,  save  its  own  unrelieved  formality,  is  in  as 
bad  taste  as  would  be  the  surrounding  of  a  mud-walled  hut  with 
architectural  balustrades  and  sculptured  ornaments.  Steep, 
formal  terraces,  without  architectural  decorations  to  unite  and 
harmonize  them  with  the  structure,  are,  unquestionably,  the 
most  insipid  and  meaningless  objects  that  can  be  introduced 
into  ornamental  grounds. 

What  is  called  an  architectural  terrace,  consisting  of  a  low 
parapet  and  balustrade  of  handsome  masonry,  or  other  rich 
ornamental  work,  has  always  a  pleasing  effect,  especially  when 
attached  to  buildings  of  an  ornamental  character,^  whether 
these  buildings  be  for  dwellings,  or  for  horticultural  purposes. 
These  terraces,  however,  are  very  different  from  those  perpen- 
dicular turf-banks,  of  which  I  have  already  spoken.  The 
former  are  truly  artistical,  and,  in  connection  with  classical 

*  The  reader  who  is  interested  in  this  subject,  and  wishes  for  further 
information  on  this  kind  of  ornamental  terraces,  is  referred  to  the  ele- 
gant remarks  and  illustrations  thereon  by  Mr.  Downing.  [See  Downing' 's 
Landscape  Gardening  ;  section,  Architectural  Embellishments.] 


SITUATION.  17 

structures,  constitute  the  harmonizing  link  between  art  in  the 
building,  and  nature  in  the  grounds.  The  latter  are  neither 
artistical  nor  natural. 

Let  the  reader  fancy  to  himself  a  horticultural  structure,  of 
unusually  large  dimensions,  situated  on  the  southern  declivity 
of  an  open  field,  without  a  single  green  leaf  of  foliage  to  inter- 
vene between  the  unbroken  whiteness  of  the  structure  and  the 
distant  sky.  The  very  ornaments  of  the  building  are  altogether 
hidden,  even  at  the  distance  of  a  dozen  yards,  because  their  forms 
are  viewed  upon  a  background  of  cloudless  vacancy;  directly  in 
front  is  a  terrace,  more  than  a  dozen  feet  deep,  and  so  steep  as 
to  require  a  ladder  to  scale  it,  and  at  the  bottom  it  terminates 
with  an  abrupt  angle,  adjoining  a  potato  and  cabbage  garden. 
However  unquestionable  may  be  the  position  of  the  splendid 
structure  here  referred  to,  there  is  something  so  irreconcilably 
incongruous  about  its  precincts,  that  the  most  untutored  imagi- 
nation is  at  once  struck  with  the  total  want  of  harmony,  unity, 
and  effect.  The  terrace  itself  has  the  unfinished  appearance 
of  a  dwelling-house,  where  the  work  has  been  suspended  before 
the  roof  and  chimneys  had  been  put  on ;  a  thing  appearing  to 
have  an  isolated  and  independent  existence,  having  no  apparent 
relation  either  to  the  structure  or  the  grounds,  and  heartily 
despised  by  both.  Now  the  position  of  the  building  referred  to 
is,  undoubtedly,  excellent,  and  a  better  site  could  not  be  found, 
to  produce  a  more  imposing  effect  from  a  front  view,  which,  in 
horticultural  structures,  is  generally  the  best,  providing  the 
structure  be  sufficiently  elevated  above  the  axis  of  vision.  But 
in  the  present  case  the  effect  is  destroyed ;  first,  by  a  total  want 
of  unity  and  harmony  in  the  foreground,  and,  secondly,  by  a  want 
of  the  deep,  dark  foliage  of  trees,  presenting  their  irregular 
outlines  against  the  sky  in  the  background,  which  gives  all 
buildings,  and  more  especially  those  of  a  light  character,  as  hot- 
houses, &c.,  that  picturesque  and  pleasing  appearance,  particu- 
larly when  the  surface  of  the  ground  is  broken  by  undulations, 
and  the  scenery  diversified  with  a  variety  of  objects,  distinct  in 
themselves,  yet  harmonizing  with  each  other. 

From  the  foregoing  observations,  the  propriety  will  be  seen 
of  placing  horticultural  erections  in  the  immediate  vicinity  of 


18  SITUATION. 

large  trees,  and  of  raising  them  where  they  do  not  already  exist. 
A  beautiful  writer  on  this  subject  has  observed,  that  green- 
houses in  the  country,  without  trees  about  them,  are  like  ships 
divested  of  their  masts  and  rigging,  and  impress  the  mind  with 
the  idea  of  their  having  wandered  from  their  right  position ; 
and,  as  Loudon  justly  remarks,  a  tree  is  the  noblest  object  of 
inanimate  nature,  combining  every  species  of  beauty,  from  its 
sublime  effect  as  a  whole,  to  the  most  minute  and  refined  ex- 
pression of  the  mind.^  We  cannot  too  strongly  urge  the  pro- 
priety of  choosing  a  site  where  these  advantages  may  be  gained. 
This  branch  of  landscape  gardening  has  been  already  treated  in 
a  masterly  manner  by  various  writers ;  therefore  we  consider  it 
unnecessary  to  dwellany  longer  upon  it.  t 

The  choice  of  position  may,  in  some  instances,  be  decided  by 
other  circumstances,  such  as  an  abundant  supply  of  water.  This 
is  indispensable,  in  hot-houses  of  every  description,  though  it 
seldom  forms  a  very  important  consideration  with  architects,  in 
their  designs,  who  are  perfectly  unconscious  of  the  amount  of 
labor  arid  expense  subsequently  created  by  a  deficiency  of  this 
element.  It  is,  therefore,  desirable  that  the  site  chosen  should 
command  a  plentiful  supply  of  water,  at  all  seasons  of  the  year, 
independent  of  what  may  be  collected  from  the  roof.  It  should 
be  considered  that  the  period  when  the  largest  quantity  of  water 
is  required  for  the  use  of  the  plants,  is  also  the  time  when  the 
supply  from  rains  is  scantiest  and  most  precarious ;  and  though 
ample  provision  must  be  made  for  collecting  all  the  water  that 
falls  upon  the  roof,  into  tanks  and  reservoirs,  suitably  and  con- 
veniently placed  for  that  purpose,  yet  this  supply  is  not  to  be 
entirely  relied  upon ;  and  hence  water  ought  to  be  conveyed  by 
pipes,  or  some  other  means,  from  the  nearest  source,  to  supply 
the  tanks  when  the  rain-water  is  exhausted. 

Where  a  stream  of  water  is  commanded  by  the  position  of 

*  Loud  on' s  Encyclopedia  of  Gardening. 

f  Those  who  wish  to  study  the  principles  of  landscape  gardening,  will 
find  all  that  is  requisite  for  their  instruction  and  improvement  in  "  Down- 
ing's  Landscape  Gardening,"  the  only  work  we  know  wherein  the  prin- 
ciples of  the  art  are  treated  in  such  a  manner  as  to  render  them  perfectly 
applicable  to  this  country. 


SITUATION.  19 

the  structure,  it  would  be  most  desirable  to  convey  it  through 
the  interior  of  the  house,  in  a  kind  of  rill,  or  small  stream,  run- 
ning through  a  shallow  channel,  or,  what  would  be  still  better, 
to  fall  into  a  tank,  over  a  small  precipice,  forming  a  little  cas- 
cade, or  water-fall.  If  the  stream  had  sufficient  power  by  its 
declivity,  a  small  jet  might  be  kept  continually  playing.  In  an 
ornamental  plant  structure,  this  would  be  the  Tie  plus  ultra  of  a 
water  supply ;  besides,  the  house  would  be  kept  delightfully 
cool  in  the  hottest  days  of  summer,  and  the  rippling  of  the 
stream  over  the  cascade,  or  the  playing  of  the  fountain,  would 
prove  the  most  agreeable  music  to  the  ear  in  the  hot  days  of 
summer. 

We  have  here  alluded  to  water,  merely  in  so  far  as  it  may 
be  likely  to  affect  the  choice  of  position.  Of  course,  water  may 
be  supplied  to  a  house  by  various  other  means,  such  as  force 
pumps,  and  that  admirable  invention,  the  water-ram,  by  which 
jets,  cascades,  &c.,  may  be  also  obtained ;  but  all  these  are  at- 
tended with  considerable  expense,  as  well  as  subsequent  labor, 
and,  therefore,  a  natural,  constant,  and  abundant  supply  of  water, 
when  possible,  should  not  be  abandoned,  even  at  the  expense  of 
some  trifling  advantages  in  other  respects.  We  have  known 
places  where  the  labor  of  carrying  the  water  for  the  different 
departments  of  the  exotic  establishment  during  summer,  exceeded 
the  labor  required  to  keep  the  garden  in  order.^ 

In  regard  to  the  precise  elevation  best  suited  for  the  site  of 
horticultural  buildings,  various  opinions  exist ;  some  prefer  low- 
lying  grounds,  others  prefer  a  considerable  altitude ;  we  have 
frequently  seen  both  parties  run  into  extremes.  Low  situations 
are  generally  warmer,  and  better  sheltered  from  boisterous  winds, 
which,  however,  is  more  than  counterbalanced  by  certain  evils 
consequent  upon  a  very  low  site.  In  spring,  low,  swampy  places 
are  always  subject  to  heavy  depositions  of  dew  and  mist,  which 
render  them  cold  and  damp,  and  expose  vegetation  of  every 
description  to  be  destroyed  by  vernal  frosts,  which  is  avoided  in 
more  elevated  situations.  We  have  this  spring  had  abundant 
evidence  of  this  fact,  in  a  very  large  tree  of  the  Platanus  Occi- 

*  For  further  information  regarding  cisterns  and  supplies  of  water, 
see  Sec.  IV.,  Internal  Arrangements. 


20  SITUATION. 

dentalis,  which  had  its  leaves  entirely  destroyed,  after  they 
were  fully  expanded,  and  are  now  strewed  upon  the  grass  be- 
neath. This  tree,  with  various  others  that  shared  the  same 
fate,  stood  in  a  low  part  of  the  pleasure  ground,  beside  a  lake. 
Trees  of  the  same  species,  on  higher  ground,  escaped  without 
injury. 

We  have  invariably  found,  in  our  experience,  that  plant-houses 
situated  in  very  low  grounds,  were  cold  and  damp  in  winter, 
and  hard  upon  the  more  tender  kinds  of  plants.  In  summer,  the 
atmosphere  is  generally  stagnant  and  unhealthy,  to  plants  as 
well  as  animals.  If  circumstances,  therefore,  afford  any  choice, 
very  low  situations  should  be  avoided,  as  it  is  more  easy,  and 
certainly  more  profitable,  to  bring  an  elevated  and  airy  situation 
into  the  condition  desired,  than  it  is  to  obviate  the  injurious 
effects  of  a  low  one. 

2.  Aspect. — We  find  that  most  people  prefer  a  southern 
aspect  for  their  hot-houses,  i.  e.,  placing  the  front  elevation  due 
south.  The  absolute  propriety  of  this  preference,  however,  de- 
serves to  be  questioned,  as  experience  has  taught  us  that  some 
valuable  advantages  are  gained  by  placing  hot-houses,  for  the 
growth  of  fruits,  on  a  south-eastern  aspect.  Let  it  be  observed, 
that  we  are  alluding  at  present  to  what  is  termed  lean-to,  or 
shed-roofed  houses,  i.  e.,  houses  having  only  one  sloping  side, —  a 
kind  of  structure  still  generally  used  for  the  production  of  grapes, 
&c.,  during  the  early  part  of  spring,  and  which  are  probably 
better  adapted  for  that  purpose  than  span-roofed  houses.  In 
fact,  we  should  prefer  a  south-eastern  aspect  for  lean-to  houses, 
whether  they  were  intended  to  grow  fruits  or  flowering  plants; 
for,  even  in  this  clear  and  comparatively  cloudless  climate,  this 
aspect  has  advantages  which,  in  our  opinion,  are  not  possessed 
by  any  other;  and,  indeed,  the  greater  intensity  of  the  sun's  rays 
at  midday  here  than  in  England,  gives  this  aspect  greater  ad- 
vantages in  this  country  than  in  any  other  where  the  sun  is  less 
powerful.  The  morning  sun  is  more  strengthening  and  exhil- 
arating to  plants  than  during  any  other  period  of  the  day,  and 
more  especially  to  plants  kept  in  houses  without  artificial  heat ; 
but  the  same  argument  holds  good  in  all  houses.  We  find  that 


SITUATION.  21 

hot-houses,  even  during  the  early  part  of  summer,  —  except  fire 
heat  be  maintained,  —  sometimes  fall  exceedingly  low  at  night, 
and  become  cold  and  chilly,  with  the  aqueous  vapors  contained 
in  the  atmosphere,  by  the  high  temperature  of  the  preceding 
day,  condensed  into  water  by  the  low  temperature  of  the  night, 
and  depending  in  small  globules  from  the  leaves  of  the  plants, 
the  under  surface  of  the  glass,  and  other  parts  of  the  house, 
rendering  the  approach  of  the  sun's  cheering  beams,  a  few 
hours  earlier  than  if  the  house  were  placed  meridionally,  above 
all  things  acceptable. 

It  might  be  plausibly  argued,  that,  if  we  take  the  south-east- 
ern aspect  for  the  purpose  of  gaining  the  morning  sun,  we  must 
lose  it  for  the  same  period  in  the  afternoon,  which,  altogether, 
makes  it  the  same  thing  to  the  house.  This  is  not  true  in  prac- 
tice ;  though  the  period  of  the  sun's  duration  upon  the  house  in 
both  cases  be  the  same,  yet  the  advantage  gained,  by  taking  the 
morning  and  losing  the  afternoon  sun,  is  very  great.  The  rays 
thus  lost  in  the  evening  are  of  little  consequence  compared 
with  those  gained  in  the  morning,  because  the  plants  are  then 
partially  enfeebled,  and  their  elaborative  powers  impaired,  if  not 
altogether  suspended,  by  the  strong  midday  heat.  By  various 
experiments  on  the  shoots  of  young  plants,  we  found  that  their 
elongation  was  greatest  during  the  mild  hours  of  the  morning, 
before  the  sun  had  attained  its  meridian  fierceness. 

In  general,  we  find  that  plants  are  more  prostrated  by  the  in- 
fluence of  the  afternoon  sun  than  during  any  other  period  of 
the  day,  and  it  is  supposed,  by  many,  that  the  sun's  heat  is  more 
powerful  and  oppressive  in  the  afternoon  —  that  is  to  say,  from 
one  to  three  —  than  it  is  when  on  its  meridian.  However  this 
fact  may  be  scientifically  supported,  it  certainly  holds  good  in 
experience.^  Supposing,  then,  that  such  is  the  case,  we  con- 

*  This  may  be  accounted  for  by  the  air  having  been  already  warmed 
to  a  high  temperature,  by  the  sun  acting  upon  it  during  the  previous 
part  of  the  day ;  and,  the  deposited  moisture  of  the  preceding  night  hav- 
ing been  already  evaporated  from  the  surface  of  the  earth,  the  lower 
strata  are  highly  rarefied.  The  hot  sun,  continuing  to  act  upon  the  lower 
stratum  of  air  and  the  dry  surface  of  earth,  gives  the  former  that  lan- 
guid, oppressive,  and  suffocating  character,  which  is  experienced  by 
every  one. 


22  SITUATION. 

sider  it  another  fact  in  favor  of  a  south-eastern  aspect,  as  the 
sun's  rays  will  thus  be  made  to  strike  the  roof  more  obliquely, 
and  will  be  less  likely  to  scorch,  or  otherwise  injure,  the  plants, 
than  if  shining  perpendicularly  to  the  plane  of  the  roof. 

Many  authors  might  be  quoted,  in  support  of  a  south-eastern 
aspect ;  and  one  of  the  best  garden  authors,  of  his  own  or  any 
other  time,  says,  "  An  open  aspect  to  the  east  is  a  point  of  cap- 
ital importance,  on  account  of  the  early  sun."  When  the  sun 
can  reach  the  garden  at  its  rising,  continuing  a  regular  and 
gradual  influence,  increasing  as  the  day  advances,  it  has  a  grad- 
ual and  most  beneficial  effect  in  dissolving  the  hoar  frost  that 
may  have  been  deposited  the  previous  night.  On  the  contrary, 
when  the  sun  is  excluded  till  about  ten  in  the  morning,  and 
then  suddenly  darts  upon  it  with  all  the  force  derived  from  its 
increased  elevation,  and  increased  power,  it  is  very  injurious, 
especially  to  fruit-bearing  plants,  in  the  spring  months.  The 
powerful  rays  of  heat  at  once  melt  the  icy  particles,  and,  imme- 
diately acting  upon  the  moisture  thus  created,  scald  the  tender 
blossoms  and  leaves,  which  droop  and  fade  as  if  nipped  by  a 
malignant  blight.^ 

These  remarks,  it  is  true,  are  by  an  English  author,  and  have 
reference  to  the  climate  of  England ;  but  they  apply  to  us  in 
full  force  in  this  country,  and,  in  many  locations  here,  are  still 
more  applicable  than  to  any  country  in  Europe. 

The  morning  sun  is  not  only  more  agreeable  to  vegetable  as 
well  as  animal  development,  but,  as  we  have  already  observed, 
vegetation  proceeds  more  rapidly  under  its  influence  than  it  does 
during  any  other  period  of  the  day.  This  may  be  accounted 
for  by  the  fact,  that  the  nourishing  gases  have  been  accumu- 
lating during  the  partial  suspension  of  elaboration  in  the  night, 
arid,  on  the  approach  of  the  sun's  vivifying  beams,  these  functions 
are  resumed  with  increased  activity,  and  continue  so,  under  the 
mild  influence  of  its  less  powerful  and  fierce  effulgence,  until 
their  energies  are  paralyzed  by  its  burning  rays,  at  midday,  when 
they  make  little  more  progress  till  the  next  morning. 

We  have  heard  similar  arguments  adduced  in  favor  of  a  south- 

*  Abercrcmbie's  Practical  Gardener. 


SITUATION.  23 

western  aspect  for  late  houses,  and  these  facts  have  regulated 
the  erection  of  some  extensive  houses  with  which  we  are  ac- 
quainted. In  this  country,  however,  hot-houses  are  seldom 
erected  for  the  express  purpose  of  retarding  grapes,  or  other 
fruits,  although  we  have  no  doubt  that  very  late  grapes  would 
pay  better  than  early  ones,  since  there  would  be  very  little  ex- 
pense in  their  production.  The  sun's  rays  in  this  climate  are 
so  powerful,  that  the  difference  in  aspect  may  not  be  so  percep- 
tible, in  regard  to  late  and  early  forcing,  as  in  England ;  still 
we  have  no  doubt  the  difference  will  be  found  sufficient  to  justify 
the  erection  of  houses  for  these  purposes,  on  the  aspects  we  have 
pointed  out  as  being  most  suitable  for  each. 

In  the  erection  of  span-roofed  houses,  that  is,  houses  with 
double  roofs,  it  makes  very  little  difference,  in  the  opinion  of 
many,  which  way  the  house  may  stand,  and,  upon  the  whole, 
the  arguments  hitherto  used,  in  favor  of  one  aspect  over  another, 
have  been  so  feeble  as  hardly  to  deserve  any  consideration. 
Supposing  the  house  to  be  a  parallelogram,  or  long  square,  with 
both  gables  glazed,  as  well  as  the  sides  and  roof,  then,  we  think, 
it  may  stand  any  wiy  in  which  the  nature  of  the  site,  or  taste 
of  the  erector,  may  dictate.  Light  being  the  most  important 
point  of  attention  in  the  construction  of  hot-houses,  these  are 
better  adapted  for  plant-growing  than  those  whose  transparent 
surface  forms  only  a  segment  of  their  transverse  section. 

As  a  general  principle,  provided  other  circumstances  are  fa- 
vorable, we  would  recommend  the  house  to  stand  north  and  south, 
with  its  longer  elevations  towards  the  east  and  west ;  we  find 
this  to  be  the  opinion  of  some  of  the  best  gardeners  in  the  coun- 
try, with  which  we  fully  agree.  If  any  advantage  be  gained  by 
placing  the  house  in  one  direction,  in  preference  to  another,  we 
think  it  is  the  one  mentioned,  as  the  rays  of  the  meridian  sun 
will  then  strike  the  glass  in  an  oblique  direction,  and  have  less 
power  than  if  they  were  to  fall  upon  the  glass  at  right  angles 
to  it.* 

The   aspect   of  conservatories   attached   to   dwelling-houses 

*  For  more  detailed  information  on  this  matter,  see  Sec.  II.,  Design 
and  Slope  of  Roof. 
3 


24  SITUATION. 

must  be  regulated  by  the  position  of  the  building,  or  the  fancy 
of  the  architect.  These  are  deplorable  erections,  generally; 
nine  tenths  of  them  unsuitable,  in  the  superlative  degree,  not 
for  want  of  cost,  but  for  want  of  skill.  As  the  remarks  we  have 
to  make,  on  this  part  of  our  subject,  belong  to  the  next  sec- 
tion, we  will  just  add  here,  that  a  conservatory  ought  never 
to  be  placed  on  the  northern  aspect  of  a  building,  nor  situated 
in  such  a  manner,  in  relation  to  the  dwelling-house,  that  the 
sun's  rays  may  be  prevented  from  falling  on  the  conservatory 
during  at  least  one  half  the  day. 


SECTION    II. 

DE  SIGN  . 

1.  General  Principles.  —  To  ascertain  principles  of  action, 
it  is  always  necessary  to  begin  by  considering  the  end  in  view. 
The  object  or  end  of  hot-houses  is  to  form  habitations  for  vege- 
tables, and  either  for  such  exotic  plants  as  will  not  grow  in  the 
open  air  of  the  country  where  the  structure  is  to  be  erected,  or 
for  such  indigenous  or  acclimated  plants  as  it  is  desired  to  force 
or  excite  into  a  state  of  vegetation,  or  accelerate  in  their  pro- 
gress to  maturity,  at  extraordinary  seasons.  The  former  class 
of  structures  are  generally  denominated  green-houses,  or  botanic 
stoves,  in  which  the  object  is  to  imitate  the  native  clime  and 
soil  of  the  plants  cultivated ;  the  latter,  comprehending  forcing- 
houses  and  culinary  stoves,  in  which  the  object  is  to  form  an 
exciting  climate  and  soil  on  general  principles,  and  to  imitate 
particular  climates. 

The  chief  agents  of  vegetable  growth  in  their  natural  habita- 
tions are  light,  heat,  air,  soil,  and  moisture;  and  the  merit  of 
managing  these  structures,  and  the  success  of  cultivating  vege- 
tables in  them,  depend  on  the  perfection  with  which  nature  in 
these  respects  is  imitated. 

To  carry  out  the  imitation  to  perfection,  or  anything  like  an 
approach  to  it,  it  is  absolutely  necessary,  as  we  have  previously 
observed,  to  be  acquainted  with  the  nature  and  habits  of  the 
plants  under  cultivation.  Vegetable  physiology  ought  to  form  a 
part  of  the  acquirements  of  the  hot-house  architect;  and  the 
chief  cause  of  the  great  improvement  in  these  structures,  of  late 
years,  in  England,  is  traceable  to  the  fact,  that  their  erection  is 
no  longer  left,  as  formerly,  under  the  control  of  mansion  archi- 
tects, as  they  are  at  the  present  day  throughout  the  length  and 


26  DESIGN. 

breadth  of  the  United  States ;  and  the  chief  reason  why  we  see 
horticultural  structures  erected  so  numerously  in  this  country, 
in  violation  of  the  first  principles  of  plant  culture,  is  undoubt- 
edly due  to  the  same  cause.  The  conservatory  is  generally  left 
to  the  uncontrolled  management  of  the  architect,  who,  of  course, 
makes  this  structure  to  correspond  with  the  rest  of  the  building, 
without  giving  the  slightest  consideration  to  the  vegetable  beings 
that  are  to  grow  in  it.  If  we  consider  this  matter  in  its  dif- 
ferent bearings,  giving  to  professional  architects  the  justice 
which  is  due  them,  it  would  be  somewhat  unreasonable  to 
expect  them  to  plan  conservatories  otherwise.  An  architect  is, 
by  education,  taught  to  study  and  apply  principles  in  his  art, 
which,  when  carried  into  effect,  as  we  sometimes  see  them  in 
the  construction  of  plant-houses,  are  in  direct  opposition  to  those 
laws  which  nature  has  laid  down  and  determined  as  essential 
to  the  vigorous  development  of  vegetable  life.  Can  it  be 
expected,  then,  that  an  architect  will  tamely  surrender  the  grand 
principles  of  his  art,  —  the  antiquity  of  which  is  coeval  with 
Cheops,  and  which  has  been  the  boast  and  pride  of  the  greatest 
empires  of  the  old  world,  —  in  meek  submission  before  the  yet 
half-developed  principles  of  vegetable  physiology,  or  even  to  the 
humble  dictates  of  practical  gardening  ?  To  expect  such  a  con- 
cession would  be  tantamount  to  expecting  an  architect  to  build 
dwelling-houses  with  drawing-rooms  solely  adapted  for  the 
accommodation  of  plants,  altogether  irrespective  of  other  pur- 
poses to  which  drawing-rooms  are  generally  applied.  Hence, 
we  find  the  conservatory  placed  just  where  it  is  most  subservi- 
ent to  the  general  design  of  the  mansion,  most  frequently  in  a 
corner  or  recess  of  the  main  building,  having  two  or  three  sides 
of  solid  opaque  material !  To  civil  architecture,  as  far  as 
respects  mechanical  principles,  or  the  laws  of  the  strength  and 
durability  of  materials,  they  are  certainly  subject,  in  common 
with  every  other  species  or  description  of  edifice ;  but  in  respect 
to  the  principles  of  design  and  beauty,  the  foundation  of  which 
we  consider,  in  works  of  utility  at  least,  to  be  "  fitness  for  the 
end  in  view,"  they  are  no  more  subject  to  the  rules  of  civil  archi- 
tecture than  is  a  ship  or  a  fortress  ;  for  those  forms  and  combi- 
nations of  forms,  and  that  composition  of  building,  which  is 


DESIGN.  27 

very  fitting,  and,  perhaps,  beautiful,  in  a  habitation  for  man  or 
for  domestic  animals,  is  by  no  means  fitting,  and  consequently 
not  beautiful,  in  a  habitation  for  plants.  Such,  however,  is  the 
force  of  habit  and  professional  bias,  that  it  is  not  easy  to  con- 
vince architects  of  this  truth.  Structures  for  plants  are  consid- 
ered by  them  no  farther  beautiful  than  as  they  display  some- 
thing of  architectural  forms,  which,  according  to  the  innumerable 
illustrations  presented  to  us,  consist  of  a  solid  opaque  building ; 
for  it  is  an  undeniable  fact  that  what  are  called  fine  architectu- 
ral conservatories,  are  designed,  not  for  the  purpose  of  growing  or 
exhibiting  flowering  plants,  for  they  have  not  even  the  appear- 
ance of  adaptation  for  this  purpose.  One  half  of  their  entire 
surface  is  obscured  by  pilasters,  blocking-courses,  cornices,  projec- 
tions, massive  astragals,  sash-bars,  etc.,  until  the  transparent  glass 
forms  only  a  small  fraction  of  the  surface  ostensibly  appropriated 
to  the  transmission  of  light.  To  complete  the  opacity  of  the 
structure,  the  whole  is  obscured  or  shaded  one  half  the  day  by 
the  main  building.  There  is  no  ideal  exaggeration  here ;  they 
form  the  grand  rule  in  ornamental  conservatories,  and  the 
exceptions  are  few.  Let  us  take,  for  example,  the  splendid  con- 
servatory erected  by  J.  W.  Perry,  Esq.,  at  his  mansion  at  Brook- 
lyn, near  New  York,  and  figured  in  Downing's  Landscape  Gar- 
dening, which  is  extolled  as  one  of  the  most  beautiful  conservato- 
ries in  the  country,  and  with  some  degree  of  justice,  for  it  is  both 
more  beautiful  and  better  adapted  for  the  purpose  than  many 
others  to  which  we  can  allude.  Yet,  beautiful  and  fit  as  it  may 
be  considered,  there  never  was,  and  never  will  be,  a  plant  grown 
in  it  to  perfection,  nor  is  it  possible  by  any  species  of  care  or 
skill  to  do  so  in  such  a  structure. 

We  have  taken  the  liberty  of  particularizing  this  conserva- 
tory, because  it  has  been  made  the  model  of  various  others 
which  we  are  acquainted  with ;  and  we  justify  our  allusion  to  it 
on  the  following  grounds :  because  the  house  in  question  has 
been  figured  and  commended  by  such  an  able  authority,  and 
consequently  been  regarded  as  a  model  of  perfection  by  many 
who  know  not  the  difference  between  a  structure  "  fit  for  the 
purpose,"  and  one  merely  beautiful  in  itself;  and,  moreover, 
because  we  are  well  acquainted  with  the  structure  itself,  as  well 
3* 


28  DESIGN. 

as  with  the  able  and  excellent  gardener  who  has  managed  it  for 
many  years,  and  who  finds  it  impossible  to  grow  plants  within, 
and  has  long  since  given  up  the  case  as  utterly  hopeless ;  the 
only  result  which  could  be  expected. 

It  may  seem  strange  that  ten  or  twelve  thousand  dollars 
should  be  expended  upon  a  plant-house,  and,  after  all  the 
expense,  the  house  be  unfit  for  the  growth  of  plants,  and  that 
this  fitness  could  be  more  extensively  obtained  at  one  twentieth 
the  cost.  Such,  however,  is  the  case,  and  will  continue  to  be 
so,  till  the  design  be  considered  in  relation  to  "  fitness  for  the 
end  in  view ;"  and  that  this  is  far  from  being  the  case,  we  have 
lately  experienced  sufficient  proof.  Buildings  like  that  we  have 
just  alluded  to,  may  properly  be  called  beautiful  specimens  of 
architecture,  but  if  the  principles  of  design  or  beauty  be  regarded 
on  fitness  for  the  end  in  view,  —  as  we  believe  it  to  be  in  works 
of  utility,  —  then,  as  plant-conservatories,  these  structures  ought 
to  be  condemned. 

I  have  no  doubt  some  of  our  architectural  readers,  and  lovers 
of  dull,  massive,  gorgeous,  and  grotesque  conservatories,  will 
pronounce  against  such  a  violation  of  the  principles  of  architec- 
ture, as  would  undoubtedly  be  perpetrated  by  building  a  mere 
shell  of  glass  to  form  a  counterpart  of  the  solid  masonry  of  a 
large  mansion.  Conversing  on  this  point  lately  with  a  talented 
architect,  he  said,  "  Conservatories  can  never  be  reconciled  with 
mansion  architecture  if  they  must  be  erected  upon  such  princi- 
ples ;  the  thing  is  utterly  inconsistent  with  beauty  in  a  building. 
Such  an  appendage,"  said  he,  "  would  be  as  absurd  as  putting  a 
gauze  covering  over  a  buffalo  robe  to  withstand  a  snow  storm." 
It  would  be  useless  here  to  reply  to  the  injustice  and  inapplica- 
bility of  these  observations,  and  we  will  let  them  go  for  what 
they  are  worth.  They  serve,  however,  to  convey  a  pretty  accu- 
rate idea  of  the  estimation  in  which  architects  hold  the  principles 
of  plant  culture,  even  when  pointed  out  to  them;  or,  as  we  might 
term  it,  how  little  they  care  for  the  beauty  expressed  by  "  fitness 
of  purpose."  Utility,  however,  is  undoubtedly  the  basis  of  all 
beauty  in  works  of  use,  and,  therefore,  the  taste  of  architects,  so 
applied,  may  safely  be  pronounced  as  radically  wrong. 


DESIGN. 


2.  Light.  —  In  erecting  horticultural  structures  of  any 
description,  the  first  and  decidedly  the  most  important  object  to 
be  kept  in  view,  is  the  introduction  of  light ;  and  really,  though 
this  point  presents  itself  to  architects  in  its  simplest  and  plainest 
reality,  it  appears  to  be  scarcely  ever  fully  considered ;  at  least, 
we  are  induced  to  conclude  so,  from  the  instances  already  before 
us.  It  is  easy  for  any  person  to  satisfy  himself  of  the  wonder- 
ful effects  of  light  upon  vegetables  under  artificial  culture,  by 
the  most  familiar  illustrations.  When  plants  are  placed  against 
a  wall,  or  other  opaque  body,  they  will  speedily  turn  the  sur- 
face of  their  leaves  to  the  light,  although  the  medium  of  its 
entrance  should  be  many  yards  distant.  One  of  the  principal 
reasons  why  plants  thrive  so  badly  in  dwelling-houses,  is  in 
consequence  of  their  being  deprived  of  that  supply  of  light 
which  is  essential  to  their  development.  Set  a  plant  how  or 
where  you  will,  it  will  twist  and  turn  itself  in  any  direction  for 
the  purpose  of  presenting  its  leaves  to  the  light,  or  to  the  aper- 
ture where  it  enters  unobstructed.  Pure  air  is  also  a  most  essen- 
tial element  in  the  economy  of  vegetation ;  but  we  may  safely 
assert,  after  much  experience,  that  plants  under  artificial  culture 
suffer  far  more  from  a  deficiency  of  light  than  from  a  deficiency 
of  what  is  called  pure  air.  The  reason  of  this  appears  obvious. 
By  the  latter  deficiency  a  plant  is  merely  deprived  of  its  neces- 
sary food ;  but  by  the  former  deficiency  the  plant  is  entirely 
deprived  of  its  vegetable  functions,  or  its  energies  are  so  en- 
feebled as  to  be  incapable  of  assimilation.  We  are  not  speaking 
here  of  light  merely  as  distinguished  from  darkness,  for  we  are 
told,  upon  good  authority,  that  the  luminiferous  ether  is  radiated 
in  all  directions  from  its  grand  source,  viz.,  the  sun,^  but  of 
its  properties  and  influence  on  plants  when  transmitted  through 
a  transparent  medium,  such  as  glass.  Every  gardener  knows 
that  plants  will  not  only  fail  to  thrive  without  much  light,  but 
will  not  thrive  unless  they  receive  its  direct  influence  by  being 
placed  near  the  glass.  The  cause  of  this  last  fact  has  never 
been  satisfactorily  explained.  It  seems  probable  that  the  glass, 

*  Principles  of  Chemistry,  by  Prof.  Silliman,  Jr. 


30 


DESIGN. 


acting  in  some  degree  like  the  triangular  prism,  partially  decom- 
poses or  deranges  the  order  of  the  rays. 

The  theory  of  the  transmission  of  light  through  transparent 
bodies  is  derived  from  the  well-known  law  in  optics,  that  the 
influence  of  the  sun's  rays  on  any  surface,  both  in  respect  to 
light  and  heat,  is  directly  as  the  sine  of  the  sun's  altitude, 
or,  in  other  words,  directly  as  its  perpendicularity  to  that  sur- 
face. If  the  surface  is  transparent,  the  number  of  rays  which 
pass  through  the  substance  is  governed  by  the  same  laws. 
Thus,  if  one  thousand  rays  fall  perpendicularly  upon  a  surface 
of  the  best  crown  glass,  the  whole  will  pass  through,  excepting 
about  a  fortieth  part,  which  the  impurities  of  even  the  finest 
crystal,  according  to  Bouquer,  will  exclude.  But  if  these  rays 
fall  at  an  incidental  angle  of  75°,  two  hundred  and  ninety-nine 
rays,  according  to  the  same  author,  will  be  reflected.  The  inci- 
dental angle,  it  will  be  recollected,  is  that  contained  between  the 
plane  of  the  falling  or  impinging  ray  and  a  perpendicular  to 
the  surface  on  which  it  falls.^ 

In  building  a  green-house  or  conservatory,  then,  light  ought 
to  form  the  first  point  of  importance,  as  success  in  plant  culture 
is  entirely  subservient  to  it,  and  we  know  full  well,  from  experi- 
ence, that  no  skill,  however  perfect,  and  no  attention,  however 
zealous,  will  compensate  for  a  deficiency  of  light.  Indeed,  no 
contingent  or  permanent  advantage  can  justify,  to  the  rnind  of 
the  experienced  gardener,  the  adoption  of  one  inch  of  opaque 
material  in  the  sides  and  roof  of  a  horticultural  building;  and 
no  part  of  the  structure,  from  the  side-shelves  and  upwards, 
should  be  rendered  opaque  that  can  consistently  be  covered  with 
a  material  capable  of  admitting  the  rays  of  light.  For  pillars 
and  other  appendages  of  strength,  the  material  ought  to  be  as 
light  as  is  consistent  with  strength  and  durability  in  the  struc- 
ture; and,  although  we  do  not  recommend  such  an  erection 
adjoining  a  dwelling-house,  experience  has  taught  that,  both  in 
this  country  and  in  others,  a  mere  shell  of  glass,  so  to  speak,  is 
not  only  the  cheapest,  but  also  the  best  adapted  for  the  artificial 
culture  of  all  kinds  of  plants,  both  for  fruiting  arid  flowering; 

*  See  Inclination  of  Hot-house  Roofs. 


DESIGN.  31 

i.  e.,  plants  that  are  cultivated  solely  either  for  their  flowers  or 
for  their  fruit. 

The  exact  manner  in  which  light  acts  upon  plants  has  been 
studied  by  Dr.  Daubeny,  and  others,  and  especially  Mr.  Hunt. 
The  result  of  these  inquiries  is  given  thus,  in  the  Gardener's 
Chronicle,  of  August  16th,  1845  :  "  Assuming,  with  Sir  David 
Brewster,  that  the  prismatic  spectrum  consists  of  only  three 
primitive  colors,  namely,  red,  yellow,  and  blue,  it  is  ascertained, 
by  experiment,  that  the  maximum  of  heating  power  is  found  on 
the  confines  of  the  red  rays  ;  that  the  largest  amount  of  light 
is  given  by  the  yellow  rays  ;  and  that  the  chemical  power  exists 
most  strongly  amidst  the  blue  rays,  of  the  spectrum.  If  we  take 
a  deep  red  glass,  which  has  been  colored  with  the  oxide  of  gold, 
it  will  be  found  that  the  quantity  of  light  which  passes  through  it 
is  very  small ;  and,  by  using  photographic  paper,  it  may  be  ascer- 
tained that  the  amount  of  that  principle  which  produces  chemi- 
cal change  is  also  very  little,  whereas  the  heat  rays  suffer  no 
interruption.  A  deep  yellow  glass,  or  a  cell  filled  to  the  thick- 
ness of  an  inch  with  a  solution  of  bicromate  of  potash,  intercepts 
the  chemical  rays,  but  admits  of  the  permeation  of  all  the  lumi- 
nous rays,  and  offers  but  little  interruption  to  the  calorific  rays. 
If,  however,  we  cover  a  pane  of  this  yellow  glass  with  another 
of  pale  green  bottle  glass,  the  passage  of  the  heating  rays  is 
much  impeded.  A  deep  blue  glass,  such  as  is  used  for  finger- 
glasses,  colored  with  oxide  of  cobalt,  or  a  solution  of  oxide 
of  copper  in  ammonia,  has  the  property  of  admitting  freely 
the  passage  of  all  the  chemical  rays,  whilst  it  obstructs  both 
the  heat  and  light  radiations.  Experiments  conducted  with 
colors  thus  obtained  led  Mr.  Hunt  to  the  following  conclusions : 

( 1 . )  Light  which  has  permeated  YELLOW  media.  LIGHT  RAYS.  — 
In  nearly  all  the  cases  the  germination  of  seeds  was  prevented, 
and  even  in  the  few  cases  where  the  germination  was  com- 
menced, the  young  plant  soon  perished.  The  germination 
seemed  referable  to  the  action  of  the  heat  rays  which  had  passed 
the  medium  employed,  rather  than  to  the  light.  Agarics,  and 
several  varieties  of  fungi,  flourished  luxuriantly  under  this  influ- 
ence. Although  the  luminous  rays  may  be  regarded  as  injuri- 


32  DESIGN. 

ous  to  the  early  stages  of  vegetation,  Mr.  Hunt  believes  that, 
in  the  more  advanced  periods  of  growth,  they  become  essential 
to  the  formation  of  woody  fibre. 

(2.)  Light  which  has  permeated  RED  media.  HEAT  RAYS.  — 
Germination,  —  if  the  seeds  are  very  carefully  watered,  and  a 
sufficient  quantity  of  water  is  added  to  supply  the  deficiency  of 
the  increased  evaporation,  —  will  take  place  here.  The  plant  is 
not,  however,  of  a  healthy  character,  and,  generally  speaking, 
the  leaves  are  partially  blanched,  showing  that  the  production 
of  chlorophyl  is  prevented.  Most  plants,  instead  of  bending 
towards  red  light,  as  they  do  towards  white  light,  bend  from  it 
in  a  very  remarkable  manner.  Plants,  in  a  flowering  condition, 
may  be  preserved  for  a  much  longer  time,  under  the  influence 
of  red,  than  under  any  other  media  ;  and  Mr.  Hunt  thinks 
that  red  media  are  highly  beneficial  under  the  fruiting  process. 

(3.)  Light  which  has  permeated  BLUE  media.  CHEMICAL  RAYS. 
—  The  rays  thus  separated  from  the  heat  and  light  rays,  and 
which  Mr.  Hunt  has  proposed  to  call  ACTIMIC,  have  the  power 
of  accelerating,  in  a  remarkable  manner,  the  germination  of  seeds, 
and  the  growth  of  the  young  plant.  After  a  certain  period,  vary- 
ing with  nearly  every  plant  upon  which  experiments  have  been 
made,  these  rays  become  too  stimulating,  and  growth  proceeds 
rapidly,  without  the  necessary  strength.  The  removal  of  the 
plant  into  yellow  rays,  or  into  light  which  has  penetrated  an 
emerald  green  glass,  accelerates  the  deposition  of  carbon,  and 
the  consequent  formation  of  woody  fibre.  It  was  also  found 
that,  under  the  concentrated  actimic  force,  seeds  will  germinate 
beneath  the  soil,  at  a  depth  in  which  they  would  not  have  grown 
under  natural  conditions.  Mr.  Hunt  believes  that  the  germina- 
tion of  seeds  in  the  spring,  the  flowering  of  plants  in  summer, 
and  the  ripening  of  fruits  in  autumn,  are  dependent  upon  the 
variations  in  the  amount  of  actimism,  or  chemical  influence,  of 
light  and  heat  in  the  solar  beam  at  these  seasons. 

It  must,  however,  be  observed,  that,  although  such  experiments 
have  much  physiological  interest,  the  value  of  them  is  greatly 
diminished  by  the  necessarily  imperfect  manner  in  which  the 
prismatic  colors  are  separated  by  artificial  preparations.  It  is 


DESIGN.  33 

almost,  if  not  quite,  impossible  to  form  pure  colors  artificially. 
The  yellow,  for  instance,  of  the  bichromate  of  potass  contains- 
both  red  and  violet  in  abundance.^ 

It  has  been  already  ascertained  that  the  amount  of  assimila- 
tion, and  consequently  of  the  healthy  exercise  of  its  vital  func- 
tions, depend  upon  the  intensity  of  the  light  to  which  the  plant 
is  exposed.  In  bright  sunshine  they  perspire  most ;  in  weak 
diffused  light,  and  in  darkness,  none  at  all.  Hales  found  that  a 
cabbage  lost  nineteen  ounces  of  weight  per  diem,  and  a  sunflower 
twenty.  He  estimated  the  average  rate  of  perspiration  by  plants 
to  be  equal  to  seventeen  times  that  of  a  man.  In  one  of  his  exper- 
iments he  found  that  the  branch  of  an  apple-tree,  two  feet  longr 
with  twenty  apples,  exposed  to  bright  sunshine,  raised  a  column 
of  mercury  twelve  inches  in  seven  minutes.  But  a  dry,  arid 
atmosphere,  especially  if  in  motion,  also  robs  the  plants  of  their 
moisture  independently  of  light. 

The  clear  and  unclouded  skies  of  this  country  do  not,  as  some 
suppose,  obviate  the  necessity  of  surrounding  the  plant  with  a 
transparent  medium  in  all  directions,  nor  does  the  dark  and  sun- 
less climate  of  England  render  it  necessary  that  the  houses 
should  be  more  transparent  there  than  here.  It  is  a  practical 
absurdity  to  fancy  that  in  England  there  is  less  light  than  in 
this  country,  and  that,  because  the  mid-day  sun  is  more  powerful, 
they  can  do  with  a  greater  opacity  of  structure.  Those  who 
make  such  statements  manifestly  know  as  little  of  the  climate 
of  England  as  of  the  natures  of  its  skies,  and  mislead  those  who 
know  as  little  as  themselves.  No  argument  whatever,  based 
upon  the  brightness  of  the  sunshine  at  mid-day,  can  serve  to 
justify  the  adoption  of  one  single  inch  of  opaque  material  in  a 
horticultural  building.  It  is  very  easy  to  reduce  the  quantity  of 
light,  or  break  the  rays  of  the  sunshine,  by  shading;  but  it  is  not 
so  easy  to  increase  the  quantity  of  light  in  the  dark  and  gloomy 
months  of  winter  ;  and  such  sort  of  plant-houses  will  damp  the 
energies  and  zeal  of  the  most  skilful  gardener,  as  well  as  his 
tender  exotics.  When  he  sees  these  errors,  which  he  cannot 
remedy,  and  observes  his  plants  speaking  in  a  language  which 

*  For  further  experiments  on  Light,  see  Sect.  IV.,  Glass. 


34 


DESIGN. 


cannot  be  mistaken,  even  by  the  most  inattentive,  "  Give  us  light, 
or  we  shall  die  !  "  he  gives  up  their  case,  in  hopeless  despair,  as 
being  altogether  beyond  his  control.  And  thus  we  have  known 
excellent  gardeners  censured  for  neglecting  things,  and  for  doing 
badly  what  it  was  not  in  their  power  to  do  better. 

Solar  influence  being  necessarily  connected  with  the  roofs  of 
hot-houses,  we  will  discuss  these  subjects  in  their  relation  to 
each  other,  including  inclination  and  reflection,  in  the  following 
sub-section. 

3.  Slope  of  hot-house  roofs.  —  In  regard  to  the  theory  of  the 
transmission  of  light  through  transparent  bodies,  we  have  already 
stated  that  the  influence  of  the  sun's  rays  on  any  surface  is 
directly  as  his  perpendicularity  is  to  tfiat  surface  ;  and,  accord- 
ing to  Bouquer,  that  if  one  thousand  rays  fall  perpendicularly 
upon  a  surface  of  glass,  the  whole  pass  through,  excepting  about 
twenty-five  rays,  or  one  fortieth  part  of  the  whole.  But  falling 
on  the  same  surface  at  an  incidental  angle  of  about  75°,  then 
two  hundred  and  ninety-nine,  or  nearly  one  third  of  them,  will 
be  reflected.  The  influence  of  the  sun  on  the  roofs  of  hot-houses 
depends  very  much  on  the  principle  there  given,  —  at  least,  so 
far  as  regards  the  form  of  its  surface.  This  principle  has  been 
applied,  in  various  ways,  for  the  purpose  of  obtaining  the  full 
influence  of  the  sun's  rays  at  certain  seasons  of  the  year.  We 
have  managed  forcing-houses  where  the  roof  was  laid  at  right 
angles  to  the  sun's  rays  in  mid-winter,  —  the  period  when  the 
most  powerful  rays  were  required  for  forcing  purposes. 

Although  it  cannot  be  denied  that  much  more  depends  on  the 
management  of  the  house,  for  the  success  of  cultivation,  than  on 
the  inclination  of  the  roof,  yet  it  is  the  most  satisfactory  method 
to  proceed  on  what  may  be  considered  something  like  princi- 
ples. And  in  this  country  we  find  this  the  more  necessary, 
because  the  heat  of  the  sun's  rays,  at  certain  seasons  of  the  year, 
is  so  violent  as  to  prove  injurious  to  vegetation  under  any  cir- 
cumstances. And  hence,  this  principle  should  be  adopted  in  the 
construction  of  hot-house  roofs,  that  their  perpendicularity  to  the 
sun's  rays,  at  the  hottest  period  of  the  year,  should  by  all  means 
be  avoided. 


DESIGN. 


35 


In  England,  the  most  common  elevation  of  roof  is  an  angle  of 
45°,  which,  in  the  latitude  of  London,  would  form  a  perpendic- 
ular to  the  impinging  ray,  about  the  beginning  of  April,  and  the 
beginning  of  September,  —  which  also  makes  the  obliquity  of 
the  rays  greatest  when  they  are  most  powerful,  viz.,  during  the 
month  of  June.  "  This  angle  is  preferred  by  most  gardeners," 
observes  Loudon,  "  probably  from  habit."  We  think,  however, 
that  something  more  than  mere  habit  justifies  the  adoption  of 
this  angle,  —  more  especially  for  forcing-houses,  —  since  by  it 
the  benefit  of  perpendicularity  is  obtained  at  a  period  when  the 
rays  are  comparatively  feeble  and  most  necessary. 

Fig.  1. 


As  some  of  our  readers  may  not  have  made  themselves  suffi- 
ciently acquainted  with  the  altitude  of  the  sun  in  relation  to  the 
slope  of  hot-house  roofs,  we  have  annexed  the  above  figure, 
(Fig.  1,)  which  represents  the  slope  of  five  different  roofs  on  the 
angles  marked  by  their  respective  complements.  /  represents 


36 


DESIGN. 


the  altitude  of  the  sun  in  the  latitude  of  London,  the  impinging 
ray  falling  on  the  roof,  c,  at  an  angle  of  45°.  It  will  be  seen 
that  the  angle,  contained  between  the  back  wall  of  the  house 
and  the  inclined  plane  of  the  roof,  c,  is  just  equal  to  the  sun's 
altitude,  —  the  one  forming  an  exact  perpendicular  to  the  other. 
Allowing,  then,  for  the  difference  of  altitude  betwixt  the 
latitudes  of  London  and  Philadelphia,  for  instance,  we  have  a 
difference  of  inclination  of  about  11°.  Hence  the  roof  of  a  hot- 
house, to  receive  the  same  influence  of  the  sun's  rays  at  that 
period,  would  be  at  an  angle  of  34°.  The  difference  will  be 
more  closely  perceived  by  the  following  cut. 

Fig.  2. 


Jn  this  cut  we  have  given  the  altitude  of  the  sun  at  Philadel- 
phia, a,  with  the  roof  at  right  angles  to  it,  on  an  angle  of  34°. 
At  b,  we  have  given  the  altitude  of  the  sun  at  London,  with  its 
corresponding  angle  of  elevation,  45°,  and,  according  to  the 
principle  here  laid  down,  both  of  these  roofs  should  be  equally 
influenced  by  the  sun,  notwithstanding  the  difference  of  his 
altitude  at  the  respective  places. 

In  a  theoretical  point  of  view  these  principles  are  correct,  and 
are  certainly  preferable  to  the  usual  mode  of  putting  on  roofs 


DESIGN.  37 

without  regard  to  anything  excepting  the  caprice  or  fancy  of  the 
architect  or  builder.  But,  as  general  principles,  we  regard  them 
as  unsafe  and  dangerous,  were  they  to  be  practically  acted  upon 
in  the  Southern  States.  Suppose,  for  instance,  the  roof  should 
be  laid  at  right  angles  to  the  sun  in  mid-summer,  —  as  is  some- 
times done  in  England,  upon  this  principle,  —  then  the  conse- 
quence would  be  that  his  rays  would  be  unendurable  by  any 
species  of  vegetation.  The  mid-summer  sun,  even  in  the  lati- 
tude of  Baltimore,  (39°  45',)  falling  on  a  transparent  surface, 
at  right  angles  to  the  impinging  rays,  would  scorch  vegetable 
forms,  and  dry  them  up  in  a  few  hours. 

It  is,  therefore,  absolutely  necessary  that  the  exercise  of  this 
principle  be  limited  to  northern  latitudes,  where  it  is  indispensa- 
ble to  economize  the  sun's  heat,  for  the  purpose  of  accelerating 
the  maturation  of  fruits.  It  may,  also,  be  applied  in  more 
southern  latitudes,  when  all  the  warmth  of  the  sun's  rays  is 
required  early  in  spring ;  and,  therefore,  if  the  principle  be 
applied  south  of  the  40°  of  latitude,  it  should  be  taken  when 
the  sun  is  at  its  very  lowest  altitude,  otherwise  the  pitch  of  the 
roof  will  be  too  flat  for  the  months  of  summer. 

We  are  decidedly  of  opinion. —  and  this  opinion  is  fully  con- 
curred in  by  some  of  the  most  learned  and  skilful  gardeners  in 
the  country  —  that  a  great  deal  of  error  is  committed  in  the 
pitch  of  hot-house  roofs ;  probably  more  than  four  fifths  of  them 
are  made  too  flat ;  their  angles  of  elevation  are  much  too  small 
for  the  climate ;  and  yet,  notwithstanding  the  fierce  heat  of  our 
perpendicular  sun  in  summer,  this  practice  is  daily  persisted  in. 
One  would  suppose  that  the  scorching  of  vine-leaves,  peaches, 
and  other  plants,  would  convince  people  of  the  impropriety  of 
erecting  their  hot-house  roofs  at  right  angles  to  the  sun's  rays 
in  any  of  the  summer  months ;  and  yet  we  know  some  of  the 
finest  graperies  in  this  country  on  angles  of  about  20°.  If  we 
consider  how  very  few  of  the  rays  are  reflected  by  the  glass,  as 
its  plane  approaches  a  perpendicular  to  the  sun's  altitude,  and 
how  many  are  reflected  as  the  angle  of  incidence  is  increased, 
we  will  then  have  some  notion  of  the  advantage  of  increasing 
the  obliquity  of  the  roof. 

The  annexed  table  will  show  the  number  of  rays  reflected 


38 


DESIGN. 


cted. 

i 

60°. 

...  112  ai 

e  reflected. 

(C 

u 

K 

1C 

(( 
11 

50°, 

...    57 

40°,    .    .    . 

...    34 

30° 

.    27 

20°,    .   .    . 

...    25 

10° 

...    25 

1° 

...    25 

from  various  angles  between  the  plane  of  the  horizon,  and  within 
two  and  a  half  degrees  of  the  perpendicular. 

Bouguer's  Table  of  Rays  reflected  from  Glass. 

Of  1000  incidental  rays,  when  the  angle  of  incidence  is 

87°  30', 584  are  reflected. 

85°, 543    " 

82°  30',  .....  474 

80°, 412 

77°  30', 356 

75°, 299 

70°, 222 

65°,    ......  175 

The  slope  of  hot-house  roofs,  therefore,  should  depend  on  the 
following  circumstances : 

The  latitude  under  which  they  are  erected.  —  If  in  a  southern 
latitude,  the  plane  of  the  roof  should  be  as  oblique  as  possible 
to  the  sun's  rays.  South  of  40°,  the  angle  of  incidence  should 
not  be  less  than  20°.  It  will  be  recollected  that  this  angle  is 
contained  between  the  sun's  rays  and  a  perpendicular  to  the 
roof. 

The  position  of  the  house,  and  the  purposes  for  which  it  is 
intended.  —  Houses  intended  for  the  forcing  of  fruits  in  winter, 
may  have  their  roofs  made  on  a  perpendicular  to  the  sun's  rays 
at  that  season.  Conservatories  attached  to  dwelling-houses  may 
also  have  their  roofs  perpendicular  to  the  rays  of  the  winter  sun, 
for  the  same  purpose ;  but  blinds  should  be  provided  for  them, 
during  the  months  of  summer,  to  guard  against  the  effects  of 
the  perpendicular  rays  when  the  sun  is  crossing  his  meridian 
altitude, 


SECTION    III. 

STRUCTUEES    ADAPTED     TO     PARTICULAR     PURPOSES. 

1.  Forcing-houses,  culinary  houses,  fyc.  —  Forcing-houses  are 
erected  with  the  intention  of  forming  an  artificial  climate  for 
the  culture  of  tender  plants  and  vegetables  in  winter  and  early 
spring.  For  this  purpose  artificial  heat  is  employed  to  keep  up 
an  exciting  temperature,  and,  therefore,  it  is  desirable  that  they 
should  be  constructed  in  relation  to  this  end. 

Until  very  lately,  the  form  in  which  forcing-houses  were  con- 
structed was  that  of  lean-to,  or  single-roofed,  houses,  with  sheds 
or  garden-offices  on  the  back  of  them.  When  it  is  not  neces- 
sary that  light  should  be  received  from  all  sides  of  the  house, 
these  lean-to  houses  answer  very  well,  and  possess  many  con- 
veniences which  cannot  be  obtained  with  span-roofs.  Climbing 
plants,  such  as  grape-vines,  trained  beneath  the  glass,  and 
peaches,  trained  in  the  same  manner,  derive  a  sufficiency  of 
light  from  the  single  roof  to  enable  them  to  bring  their  fruit  to 
perfection ;  and  it  is  very  doubtful  if  single  roofs  will  ever  be 
entirely  superseded  for  the  purposes  of  winter  forcing. 

Fig.  3. 


Fig.  3  is  the  section  of  a  pit  for  winter  forcing,  which  we 

consider  well  fitted  for  the  several  purposes  to  which  these  pits 
4* 


40  STRUCTURES    ADAPTED   TO    PARTICULAR    PURPOSES. 

may  be  applied.  The  one  here  represented  is  what  we  have 
formerly  used  for  the  culture  of  grape  vines,  French  beans,  and 
strawberries,  during  winter;  and  where  fermenting  manure  is  to 
be  had  in  abundance,  it  is  probably  the  most  economical  house 
for  this  kind  of  forcing. 

Fig.  4  is  the  plan  of  a  forcing  pit.  This  house  is  80  feet  long, 
in  two  divisions  of  40  feet  each.  It  is  chiefly  intended  for  forc- 
ing vines  in  pots,  and  is  furnished  with  a  bed,  b,  which  is  filled 
with  fermenting  materials  for  plunging  the  vines  in,  and  supplying 
them  with  bottom  heat.  A  shelf,  c,  elevated  to  within  about  20 
inches  of  the  glass,  on  the  back  wall,  and  extending  the  whole 
length  of  the  house,  is  intended  for  forcing  strawberries  in  pots ; 
d  is  another  shelf,  for  the  same  purpose,  on  the  front  wall. 

We  have  designed  this  pit  with  the  view  to  procure  the  great- 
est accommodation  in  the  given  space,  at  the  smallest  expenditure 
for  construction,  keeping  strictly  in  view  the  purposes  for  which 
it  is  intended.  For  winter  forcing,  we  decidedly  approve  of  this 
kind  of  house  above  all  others,  i.  e.,  where  utility  only  is  consid- 
ered in  regard  to  it.  The  cost  of  this  house  is  only  four  hundred 
dollars,  or  eight  dollars  per  linear  foot. 

A  house  for  winter  forcing  should  never  exceed  40  feet  in 
length,  even  where  the  operations  are  extensive.  Thirty  or  35 
feet  is  considered,  by  the  best  gardeners,  the  most  desirable 
length.  If  the  range  be  a  greater  length,  and  the  operations 
very  extensive,  it  should  be  subdivided  into  either  of  the  dimen- 
sions here  stated,  and  each  division  heated  by  a  separate  appara- 
tus. 

There  is  no  branch  of  gardening  that  requires  a  greater  amount 
of  skill,  or  is  more  calculated  to  display  the  mastership  of  the 
gardener's  art,  than  winter  forcing.  It  is  absolute  folly  for  any 
novice  in  gardening  to  attempt  it.  To  be  successful  in  produc- 
ing the  luxuries  of  summer,  in  winter  or  early  spring,  requires  a 
great  degree  of  skill,  vigilance,  constant  and  persevering  energy. 
The  most  unwearied  attention  is  requisite,  from  the  day  the 
house  is  started  into  work,  until  the  productions  are  all  fully 
matured.  Scarcely  a  day  passes  but  something  happens,  tend- 
ing to  thwart  the  object  of  our  labors.  Heat  or  cold,  wind  or 


STRUCTURES   ADAPTED   TO    PARTICULAR    PURPOSES.  41 


'14,  STRUCTURES   ADAPTED    TO    PARTICULAR    PURPOSES. 

steam,  moisture  and  drought,  mice,  worms,  slugs,  aphides,  and 
insects  innumerable,  as  Cowper  says,  oft  work  dire  disappoint- 
ment, that  admits  no  cure,  and  which  no  care  can  obviate.  It 
is,  therefore,  the  more  requisite  that  the  structure  intended  for 
these  purposes  should  be  the  best  that  science  and  practice  can 
adopt. 

Fig.  5  is  the  end  section  of  a  forcing-stove,  which  we  have 
seen  used  in  various  parts  of  this  country,  with  considerable  suc- 
cess. It  is  sunk  a  few  feet  into  the  ground,  so  that  the  roof 
reaches  within  about  two  feet  of  the  ground  level.  lu  some 
places  this  kind  of  pit  answers  very  well,  as  in  very  dry  and 
sheltered  situations.  The  site  of  such  a  pit  must  necessarily  be 
in  gravel,  or  sand;  in  wet  clay,  coldness  and  dampness  would  be 
unavoidable ;  and  in  exposed  situations,  it  would  be  very  unsuit- 
able for  winter  forcing,  unless  provision  were  made  for  covering 
it  at  night. 

Fig.  5. 


Fig.  6  shows  the  end  section  of  a  polyprosopic  forcing-house, 
which,  by  some,  is  considered  superior  to  all  other  forms  for 
winter  forcing.  The  roof  presents  the  different  faces  to  the  sun's 
rays,  <z,  a,  a,  at  different  periods  of  the  year.  This  kind  of  roof 
may  be  considered  as  exactly  equivalent  to  a  curvilinear  figure, 
whose  curved  lines  shall  touch  all  the  angles  of  the  faces,  so  that, 
were  the  house  built  in  the  form  of  a  semi-ellipse,  or  having 
curved  ends,  the  sun  would  be  nearly  perpendicular  to  some  one 
of  the  faces  every  hour  of  the  day,  and  every  day  in  the  year. 

The  rafters  in  this  house  are  curved  the  same  as  in  a  curvi- 


Fig.  6. 


44      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

linear  house,  and  should  be  made  of  iron,  as  a  curvature  for  this 
purpose  can  be  made  cheaper  of  iron  than  of  wood,  and  is 
tighter  and  more  durable.  Iron  beams  are  made  to  screw  into 
the  rafters,  b,  b,  b,  £,  having  a  fillet  in  which  the  smaller  rafters 
are  placed,  on  which  the  sashes  run.  We  have  seen  two  methods 
of  constructing  this  kind  of  roof,  —  the  one  just  described,  in 
which  the  sashes  are  made  to  slide,  and  another,  in  which  the 
sashes  are  made  to  rise  on  hinges,  by  which  the  house  may  be 
aired,  over  the  whole  surface  of  the  roof,  or  entirely  exposed,  for 
admission  of  a  congenial  shower  of  rain,  or  for  hardening  the 
vines  or  peach  trees,  after  the  crop  has  been  gathered.  The 
arrangement  by  which  this  is  effected  is  exceedingly  simple,  not 
liable  to  get  out  of  repair,  and  is  applicable  to  all  kinds  of  houses, 
whether  the  roof  is  formed  of  curved  or  straight  lines.  This 
form  of  house  is  considered  by  Loudon  as  the  ne  plus  ultra  of 
improvement,  so  far  as  air  and  light  are  concerned.  We  are  of 
opinion,  however,  that  these  considerations  alone  render  it  less 
valuable  in  this  country  than  it  is  in  England,  except,  as  we 
have  already  stated,  for  the  purposes  of  winter  forcing. 

The  Cambridge  pit,  Fig.  7,  is  admirably  adapted  for  early 
forcing,  where  there  is  an  abundant  supply  of  stable  manure. 
It  is  heated  entirely  with  fermenting  material,  and  is  much  used 
in  England  for  the  purpose  of  growing  pine-apples,  melons, 
cucumbers,  &c.  a,  #,  are  shutters,  which  lift  entirely  off,  or  are 
wrought  up  and  down  by  hinges  attached  to  the  back  wall  of 
the  pit.  These  shutters  are  made  to  fit  closely  on  the  lining 
bed,  b}  b,  which  is  kept  constantly  filled  with  the  materials  to 
supply  the  heat,  which  enters  the  interior  of  the  pit  through 
pigeon-holes  in  the  wall.  We  have  kept  pines  during  long  and 
severe  winters,  in  this  kind  of  pit,  keeping  up  a  temperature  of 
50°  to  55°  in  the  coldest  weather.  During  winter  the  linings 
require  to  be  frequently  renewed,  at  least  every  week  some  fresh 
material  must  be  added,  otherwise  the  heat  will  decline  below 
the  minimum  temperature  ;  and,  as  it  will  be  some  time  before 
the  new  linings  generate  much  heat,  a  part  should  only  be  re- 
newed at  one  time,  and  never  both  sides  of  the  pit  at  once. 

Saunders'  forcing-pit,  Fig.  8,  is  considered  an  improvement 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      45 

upon  the  foregoing.  This  pit  has  a  double  roof,  and  is  furnished 
with  the  dung-beds,  a,  a,  on  each  side  of  the  house.  The  fer- 
menting material  is  supplied  by  means  of  linings  along  both 
sides  of  the  pit,  and  communicates  the  heat  to  the  beds  through 
the  arches  in  the  side  walls.  This  pit  has  a  narrow  path  in 
the  centre,  which  admits  of  the  internal  operations  being  carried 
on  with  more  facility.  We  have  only  seen  this  pit  in  use  by 
the  inventor,  and,  so  far  as  we  know,  it  is  quite  original.  Mr. 
Saunders  informs  us  that  it  answers  the  purposes  of  early  forc- 
ing better  than  any  other  construction  he  has  tried,  and  works 
admirably,  in  the  severest  weather,  without  the  aid  of  fire.  We 
have  the  fact  of  its  perfect  adaptability  fully  verified  by  its  pro- 
ductions, and  are  so  fully  satisfied  with  its  superiority  as  a 
dung-pit,  that  we  are  about  erecting  one  ourself.  It  ought  to  be 
borne  in  mind* regarding  this  pit,  that  unless  there  be  abundant 
supplies  of  fermenting  manure  always  at  hand  when  required, 
it  would  be  useless  to  attempt  forcing  with  it  in  winter ;  but  this 
fact  also  applies  to  all  forcing  pits  heated  solely  by  fermenting 
materials. 

Fig.  9  is  the  end  section  of  a  curvilinear-roofed  cold-pit,  for 
protecting  plants  not  sufficiently  hardy  to  stand  the  winter  with- 
out protection,  yet  hardy  enough  to  endure  a  considerable  degree 
of  cold,  and  even  a  slight  frost,  if  kept  in  a  dry  state.  Of  this 
class  we  might  name  verbenas,  roses,  pansies,  &c.  Indeed, 
there  are  many  summer  flowers,  used  by  the  amateur,  for  the 
decoration  of  his  parterre  and  flower-garden,  which  he  might 
save,  during  the  winter,  in  such  a  pit.  The  pit  here  given  we 
consider  the  best,  for  any  purpose  to  which  the  cold-pit  can 
be  applied.  We  have  found  them  practically  superior  to  all 
other  pits  we  have  yet  used ;  and  as  iron  is  now  coming  into 
general  use,  for  the  construction  of  horticultural  buildings,  we 
believe  that  these  pits  will  be  found,  not  only  the  most  convenient, 
but  also  the  cheapest  that  can  be  erected,  a,  shows  the  bed  in 
which  the  plants  are  placed  —  we  generally  put  in  about  a  foot 
deep  of  tan,  or  saw-dust,  for  plunging  the  pots  in  ;  —  b,  b,  shows 
the  sashes,  elevated  for  the  admission  of  air,  supported  by  iron 
rods,  c,  c,  which  are  made  to  enter  a  staple,  by  being  bent,  or 
hooked,  at  the  end. 


46  STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 


Fig.   9. 


Fig.  10. 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES.  47 

Fig.  10  is  a  representation  of  an  ordinary  dung-bed,  with  the 
frame  set  on  it.  The  formation  of  dung-beds  is  so  simple  as 
hardly  to  need  a  single  word  of  explanation ;  nevertheless,  a 
few  passing  remarks  may  be  useful  to  the  uninitiated. 

Hot-beds  of  fermenting  materials  are  generally  laid  on  the 
surface  of  the  ground.  Some  prefer  the  basis  of  the  bed  to  in- 
cline slightly  towards  the  horizon  ;  but  we  can  see  no  utility 
whatever  in  this  system,  except  the  site  of  the  bed  be  very  wet, 
and  then  we  prefer  building  the  bed  on  a  layer  of  brushwood. 
It  is  also  beneficial  to  place  a  layer  of  brushwood  every  eight  or 
ten  inches  deep,  which  lets  the  rank  heat  and  steam  escape 
more  readily.  The  bed  should  have  a  slight  inclination  towards 
the  south,  when  the  frame  is  laid,  though  this  rather  tends  to 
prevent  the  bed  heating  equally  all  over;  and,  where  light  is 
not  an  object,  as  in  cutting-beds,  &c.,  we  prefer  it  quite  level, 
and  even  inclining  towards  the  north,  the  inclination  of  the 
frame  turned  in  the  same  direction. 

Temporary  or  portable  frames,  or  cases,  for  covering  beds, 
and  protecting  plants,  are  exceedingly  useful  about  places  where 
it  is  requisite  to  harden  young  plants,  or  protect  individual 
specimens  in  the  open  ground. 

Fig.  11  shows  a  portable  glass  frame,  of  a  rectangular  shape, 
and  which  we  have  often  found  useful  for  hardening  young 
stock,  in  the  early  part  of  summer,  which  was  intended  for  bed- 
ding out  in  the  flower-garden.  It  can  also  be  set  on  a  dung- 
bed  for  growing  early  melons,  cucumbers,  and  starting  young 
plants  into  growth  ;  for  this  it  is  admirably  adapted,  as  the  light 
is  admissible  all  round. 

A  portable  frame  of  this  kind  may  be  made  of  any  size.  We 
find,  however,  that  about  four  feet  wide,  and  six  or  eight  feet 
long,  is  the  most  convenient  size  for  practical  purposes. 

Fig.  12,  the  portable  plant  protector,  which  will  be  found 
exceedingly  useful  for  covering  individual  plants,  standing  in 
the  open  ground.  Those  may  be  glazed  with  coarse  glass,  or 
covered  with  oil-cloth.  They  will  be  found  of  much  utility  in 
covering  the  more  tender  conefirs  during  winter,  as  well  as  dur- 
ing summer  from  the  intense  heat.  By  having  the  south  side  of 
the  case  painted  with  a  slight  coat  of  a  lime  solution,  to  darken 
5 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 


Fig.  12. 


Fig.  11. 


Fig.  8. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      49 

the  glass  and  prevent  the  entrance  of  the  solar  rays  in  that 
direction,  the  plants  are  better  able  to  endure  the  extremes  of 
either  heat  or  cold,  than  if  exposed  or  covered  with  straw  or 
mats. 

In  using  these  protectors  for  winter  covering,  it  is  only  neces- 
sary to  throw  a  garden  mat  over  the  case  during  severe  frosts, 
removing  it  when  the  weather  becomes  mild,  or  immediately  on 
the  relaxation  of  the  frost.  There  is  not  the  slightest  injury 
resulting  from  the  taking  off  the  mats,  as  would  be  the  case  with 
mat  and  straw  coverings  without  the  protector,  as  a  body  of  air 
is  always  at  rest  inside,  which  prevents  the  temperature  from 
falling  so  low  as  to  cause  injury  to  the  tree. 

Framing-Ground.  —  This  term  seems  to  have  a  very  different 
meaning  in  American  gardens  from  what  it  has  in  England,  for 
we  find  the  spot  usually  appropriated  to  the  pits,  frames,  hot- 
beds, &c.,  located  in  some  out-of-the-way  corner,  with  dung, 
weeds,  and  rubbish  lying  about  in  all  directions,  or,  perhaps,  we 
may  observe  them  occupying  a  place  in  one  of  the  squares  of 
the  garden,  a  site  equally  objectionable. 

Where  frames  and  hot-beds  are  extensively  used,  they  should, 
by  all  means,  have  a  place  appropriated  to  themselves,  and 
sheltered,  if  possible,  on  the  east,  north,  and  west;  and,  as  we 
can  see  no  reason  why  this  department  of  the  garden  should  not 
be  visited  by  the  proprietor  as  well  as  any  other,  it  should  be 
laid  out  and  kept  in  a  manner  to  make  it  worthy  of  a  visit.  In 
fact,  the  frame-ground  should  come  as  naturally  in  the  course 
of  promenade  as  the  larger  fruit  houses.  Every  one,  indeed, 
may  not  take  the  same  interest  in  this  department  as  in  others 
of  the  garden,  but  this  can  form  no  excuse  for  huddling  the 
frames  and  hot-beds  into  some  recess,  out  of  the  way,  and  pay- 
ing no  attention  to  order  and  cleanliness  about  them.  Who, 
that  is  in  the  habit  of  frequently  visiting  large  gardens,  has 
not  heard  the  gardener  apologizing  for  the  filthy  condition  of 
his  frame-ground,  when  the  curiosity  or  interest  of  the  visitor 
led  him  thither  ?  The  only  reason  that  can  be  given  for  this 
state  of  things  is,  that  the  frame-ground  is  seldom  intended  to 
form  a  prominent  object  in  the  establishment ;  its  object  being 


50      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

altogether  for  utility,  it  is  considered  by  many  a  matter  of 
absurdity  to  make  it  also  an  object  of  beauty. 

If  gardeners  would  consider  how  much  gratification  they 
sometimes  lose  themselves,  by  depriving  this  department  of  the 
garden  of  its  interest  by  proscription,  they  would  exert  them- 
selves more  to  bring  it  forward  into  its  right  place.  If  it  is  not 
a  source  of  interest  to  others,  it  should  be  made  so  to  the  pro- 
prietor, for  it  must  not  be  forgotten,  that  the  pleasure  and  satis- 
faction derived  even  from  culinary  hot-beds  and  forcing-pits, 
does  not  wholly  consist  in  their  receiving  the  produce  thereof, 
when  ready  for  use,  —  for  if  so,  recourse  need  only  be  had  to 
the  markets,  —  but,  also,  in  marking  the  progress  of  their  devel- 
opment, from  the  commencement  to  the  close  of  their  growth, 
in  beholding  fruits  and  vegetables  flourishing  in  an  artificial 
climate,  and  in  the  satisfaction  of  partaking  of  products  of  our 
own  growth. 

When  the  ground  rises  towards  the  north  part  of  the  garden, 
this  is  doubtless  the  most  eligible  site ;  although  we  are  aware 
ttiat  some  prefer  placing  them  within  an  enclosure  inside  the 
garden,  yet  we  think  they  are  better  placed  near  the  northern 
boundary.'  As  dung  is  at  all  times  necessary,  and  at  all  times 
being  carted  to  the  frame  yard,  it  is  a  continual  nuisance  having 
it  taken  over  clean  gravel  walks.  It  is,  above  all  things,  desira- 
ble to  have  the  spot  approachable  by  carts,  without  in  any  way 
coming  upon  the  gravel  walks,  which  are  appropriated  only  to 
promenade. 

Fig.  13  shows  the  disposition  of  the  forcing-houses,  frames, 
etc.,  at  a  gentleman's  residence  in  the  country,  which  is  now 
being  executed  under  our  direction.  The  ground  on  the  north 
side  of  the  garden  rises  somewhat  abruptly  from  the  principal 
range,  which  gives  the  houses  a  fine  aspect  and  a  dry  site. 
Immediately  behind  them,  and  stretching  along  the  whole  length 
of  the  forcing-pits,  and  frame-ground,  compost-ground,  etc.,  is  a 
belt  of  trees,  which  have  been  planted  expressly  for  the  purpose 
of  sheltering  the  spot  from  the  north  and  north-eastern  winds, 
the  same  object  being  attained  by  rising  ground  and  plantation 
on  the  west.  Abundant  space  is  left  between  the  different 
erections  to  afford  room  to  promenade  and  inspect  the  whole 


5* 


52      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

department,  without  being  annoyed  with  manure  under  foot. 
Here,  also,  sheds  and  offices  have  been  erected  for  the  various 
purposes  of  the  establishment,  and  arranged  with  a  due  regard 
to  convenience  and  economization  of  labor  in  the  operations 
daily  going  on  in  this  department  of  the  garden. 

The  position  of  the  framing-ground  should  command  a  good 
supply  of  water;  either  a  natural  stream  should  be  brought 
through  it,  or  a  plentiful  supply  kept  in  a  large  tank,  as  in  the 
plan,  Fig.  13,  and  kept  always  full  for  immediate  use,  either  by 
means  of  a  water-ram,  or  other  forcing-power.  Pipes  should  be 
led  from  this  large  tank  or  reservoir  into  small  tanks,  one  of 
which  should  be  in  each  house,  to  be  kept  at  the  same  tempera- 
ture of  the  atmosphere  of  the  house  in  winter,  for  watering  the 
plants.  These  tanks  should  receive  the  water  from  the  roof, 
and  be  supplied  from  the  reservoir,  when  that  is  exhausted. 

Fig.  13  is  a  ground  plan  and  arrangement  of  frame-ground 
designed  by  the  author  for  a  gentleman's  garden. 


REFERENCE  TO  PLAN. 

a     Orange  house. 
b  b     Vineries. 
c  c    Vine-stoves  for  forcing  in  winter,  the  vines  being  grown 

in  pots. 

d  d    Culinary  stoves. 
e     Cold  frames. 
/    Water  tank. 
g     Open  shed  for  soils. 
h     Seed  room. 
i    Garden  office. 
j    Miscellaneous  store  room. 
k     Potting  room. 
.     I     Store  room  for  pots. 

m     Tool  house. 

n  n    Large  beds,  in  which  green-house  plants  are  plunged  in 
ashes  during  summer,  being  covered,  during  the 
heat  of  the  day,  with  awnings  fixed  on  rollers, 
mounted  on  a  slight  frame-work. 
U     U  it 


STRUCTURES   ADAPTED   TO    PARTICULAR    PURPOSES. 


53 


54      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

2.  Graperies,  Orangeries,  fyc.  —  These  we  have  distin- 
guished from  forcing-houses,  as  not  being  stimulated  before  their 
natural  season  of  growth,  artificial  heat  being  sometimes  applied, 
however,  for  their  protection  from  early  frosts  in  spring,  and  for 
ripening  the  fruits  or  accelerating  the  maturation  of  the  current 
year's  shoots  in  autumn. 

A  greater  latitude  may  be  taken,  in  the  construction  of  houses 
of  this  class,  both  as  regards  extent  and  ornament.  Here  the 
taste  and  wealth  of  the  proprietor  may  be  indulged  to  any 
degree.  These  structures  may  vary  in  length  from  30  to  100 
feet,  or  more,  although  we  prefer  them  to  be  limited  to  the  lat- 
ter dimensions,  adding  others  of  different  proportions,  rather 
than  continue  the  unbroken  flatness  of  the  roof  beyond  this 
extent. 

Fig.  14  represents  a  range  of  houses  of  this  class,  erected  by 
John  Hopkins,  Esq.,  in  the  gardens  of  his  splendid  country-seat 
at  Clifton  Park.  This  is  one  of  the  most  extensive  structures 
of  this  kind  yet  erected  in  this  country.  It  is  three  hundred 
feet  in  length,  by  twenty-four  in  breadth.  The  structure  is 
divided  into  three  compartments  of  one  hundred  feet  each ;  the 
centre  compartment,  which  is  larger  and  loftier  than  the  others, 
is  appropriated  to  the  growth  of  orange  trees  planted  in  the 
ground,  which,  in  a  few  years,  will  form  a  complete  orchard  of 
orange  and  lemon  trees. 

The  site  of  these  houses  is  one  for  which  nature  has  done  com- 
paratively little,  but  for  which  art  and  outlay  have  done  much, 
and  for  which  the  taste  and  munificence  of  the  proprietor  are  still 
doing  more ;  but,  like  many  other  structures  which  have  come 
under  our  observation,  they  contain  much  inferior  glass  in  the 
roof-sashes,  which  is  very  injurious  to  tender  foliage.  Bad  glass 
is  an  abundant  material  in  the  United  States,  and  is  generally 
used  by  tradesmen,  who  do  the  work  by  contract,  on  account  of 
its  cheapness.  This  is  a  matter  which  demands  particular 
attention  from  those  erecting  horticultural  buildings ;  otherwise, 
they  may  not  discover  the  error,  until  too  late  to  prevent  it. 

Fig.  15  is  a  representation  of  a  model  house  for  growing 
grapes  on  the  lean-to  or  single-roofed  system;  and,  both  in 
regard  to  its  dimensions  and  slope  of  roof,  is  just  such  a  struc- 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES.  55 


56      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

ture  as  we  would  recommend  —  that  is,  if  a  lean-to  house  was 
desired  by  the  erector,  or  the  position  would  not  admit  of  any 
other  kind.  We  need  hardly  mention  that  houses  of  this  kind 
are  suitable  in  many  positions  where  curvilinear  houses  would 
be  inappropriate,  and  where  span-roofed  houses  would  be 
impracticable.  This  house  is  at  once  cheap  and  substantial, 
in  every  way  adapted  for  grape-growing,  and  presenting  as 
good  an  appearance  to  the  spectator  as  one  that  would  cost 
double  the  sum,  without  any  corresponding  advantage. 

Fig.  16  is  a  span-roofed  house  on  the  same  scale  and  the 
same  design.  Of  course,  span-roofed  houses  are  to  be  preferred, 
either  for  plant-houses  or  for  cold  vineries,  to  lean-to  houses, 
although,  as  we  have  said,  there  are  positions  which  render 
lean-to  houses  preferable,  even  as  cold  houses.  Span-roofed 
houses  cost  somewhat  more  in  their  erection  than  single  roofs  ; 
nevertheless,  we  consider  it  a  matter  of  economy  to  erect  a 
span-roofed  house  where  the  position  is  suitable,  because  the 
difference  of  cost  is  not  so  much  as  the  difference  of  glass  sur- 
face available  for  the  growth  of  vines.  In  fact,  a  span-roofed 
house  gives  just  two  single-roofed  houses  of  the  dimensions  of 
one  of  its  sides.  Hence,  it  is  clear,  that  as  many  grapes  can  be 
grown  in  a  span-roofed  house,  50  feet  long  and  20  feet  wide,  as 
in  a  single-roofed  house,  100  feet  long  and  10  feet  wide,  while 
the  back  wall,  100  feet  in  length,  is  saved. 

From  the  principles  we  have  laid  down  for  the  construction 
of  hot-houses,  in  the  beginning  of  this  section,  it  will  be  apparent 
that  double-roofed  houses  are  in  every  way  superior  to  single 
ones  for  the  general  purposes  of  horticulture,  not  only  on  account 
of  their  superior  lightness,  but  also  as  regards  cost  of  erection. 
And  we  find  this  fact  is  now  becoming  generally  admitted,  from 
the  prevailing  tendency  to  erect  double-houses,  all  over  the 
country,  where  the  advantages  of  double  roofs  are  not  sacrificed 
to  the  desire  of  having  a  more  imposing  and  extensive  appear- 
ance from  a  single  point  of  view. 

Amongst  the  various  forms  of  curvilinear  houses  lately  brought 
under  our  notice,  is  that  of  forming  the  roof  of  the  segment  of  a 
circle,  which  shall  equal  the  width  of  the  house,  —  a  principle 
which  we  think  is  not  generally  recognized,  nor  do  we  think  it 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 


57 


58      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

applicable  except  under  certain  circumstances.  We  have  seen 
houses  erected  on  this  principle  in  Northern  Europe,  where  they 
doubtless  answer  the  purpose  much  better  than  houses  with  ellip- 
tical roofs,  for  the  reasons  already  stated  in  regard  to  forcing- 
houses;  viz.,  the  deficiency  of  perpendicular  light,*not  only  in  the 
winter  and  spring,  but  also  in  the  early  part  of  summer,  when  all 
the  perpendicular  power  of  the  sun's  rays  is  required  for  the  proper 
maturation  of  the  fruit.  It  must  be  evident,  however,  that  these 
reasons  can  be  of  no  influence  on  this  side  the  Atlantic,  at  least, 
in  the  southern  and  midland  states,  although  we  know  of  several 
houses  in  the  state  of  New  York,  built  on  this  principle,  or  a 
very  near  approximation  to  it. 

Fig.  17  is  a  single-roofed  curvilinear  house,  built  on  the  above 
principle,  the  back  wall  being  equal  to  the  breadth  of  the  house. 
As  a  single-roofed  house,  this  curve  has  a  very  good  appearance, 
and  answers  admirably  where  perpendicular  light  is  desirable. 
The  only  objection  that  can  be  urged  against  it,  is  the  flatness 
in  the  upper  portion  of  the  roof,  which  gives  it  the  same  faulty 
character,  for  our  hot  climate,  that  we  have  urged  against  the 
flat  roofs  of  straight-lined  houses. 

Fig.  18  is  intended  to  represent  a  double-roofed  house,  on  the 
same  principle.  Here  the  width  of  the  house  must  be  equal  to 
the  chord  of  both  the  sides.  The  parapet  wall  being  only  a  con- 
tinuation of  the  semi-circle,  of  course  this  form  of  house  is  open 
to  the  same  objections  as  the  other,  (Fig.  17,)  even  in  a  greater 
degree,  as  the  flat  part  of  the  roof,  in  this  case,  is  precisely 
doubled.  The  perpendicularity  of  the  rays  is  in  some  measure 
obstructed  by  a  portion  of  the  segment,  at  the  apex  of  the  roof, 
being  opaque,  as  in  the  case  of  the  house  from  which  our  sketch 
is  taken.  This  plan  answers  the  purpose  very  well,  without 
depriving  the  house  of  its  effect,  and  we  think,  where  it  is  neces- 
sary, the  effect  might  be  heightened  by  a  slight  balustrade,  or 
other  ornament. 

That  curvilinear  houses,  properly  constructed,  are  superior  to 
those  with  plain  roofs,  can  hardly  be  questioned  on  practical  or 
scientific  grounds.  The  construction  of  the  monster  palm  house, 
lately  erected  in  Kew  Gardens,  at  London,  is  an  evidence  that 
this  principle  is  recognized  by  the  most  scientific  cultivators  in 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      59 

that  kingdom ;  and  though  the  immense  structure  is  avowedly 
for  the  growth  of  palmaceous  plants,  still  the  objections  that 
might  be  urged  against  its  modification  as  a  palm-house  might, 
with  equal  propriety,  be  urged  against  its  form  as  a  fruit  house,. 
on  a  smaller  scale.  If  there  be  any  fault  in  its  curvilinear  con- 
struction, the  fault  is  augmented  as  the  dimensions  of  the 
structure  are  increased. 

The  objections  that  have  been  urged  against  curvilinear 
houses  in  England  can  have  little  application  in  this  country, 
whatever  force  they  might  have  in  the  cloudy  climate  of  North- 
ern Europe.  And  we  cannot  help  thinking  that  the  arguments 
against  them  have,  in  a  great  degree,  promoted  their  adoption,, 
on  account  of  the  inconsiderate  manner  in  which  their  mode  of 
structure  has  been  questioned.  We  think  it  clear,  that  any  form 
of  curvilinear  roof,  from  the  common  rectangle  to  the  semi- 
ellipse,  or  the  acuminated  semi-dome,  not  only  admits  of  a  larger 
run  of  roof,  but  also  a  larger  proportion  of  light,  than  any  form 
of  straight-lined  roof  that  can  be  adopted,  excepting  the  polypro- 
sopic  roof,  which,  in  fact,  is  nothing  more  than  an  approximation 
to  the  curvilinear,  or  spherical  roof,  having  the  advantages  of 
the  one,  without  the  disadvantages  of  the  other. 

Another  remarkable  property  possessed  by  curvilinear  roofs, 
and  not  by  straight-lined  ones,  is  their  power  of  reflection  and 
refraction,  which,  in  the  hot  summers  of  our  climate,  is  of  much 
more  importance,  in  a  horticultural  point  of  view,  than  is  gener- 
ally supposed.  Though  the  power  of  curved  surfaces  of  reflect- 
ing the  rays  of  light  be  similar  to  that  of  plane  surfaces,  yet  the 
plane  is  so  small  on  which  the  rays  fall,  that  its  position  is  changed 
before  its  concentration  can  cause  injury  to  the  foliage  on  which 
it  falls.  As  the  surfaces  of  curvilinear  roofs  are,  or  ought  to  be, 
presented  more  obliquely  to  the  sun's  rays  than  straight-lined 
roofs,  the  amount  of  refraction,  in  very  hot  weather,  will  be 
greater  in  the  former  than  in  the  latter  case.  The  more  ob- 
liquely the  ray  falls  on  the  medium  of  refraction,  the  greater  the 
amount  refracted. 

The  general  form  of  curvilinear-roofed  houses,,  in  this  country, 
is  the  common  curvature  already  described,  forming  the  segment 
of  an  ellipse,  the  ends  being  upright  as  in  straight-lined  houses. 
-      6 


60  STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 

For  the  purposes  of  grape-growing,  we  think  a  loss  of  surface  is 
sustained  by  the  position  of  the  gable  ends.  In  fact,  from  a  series 
of  calculations,  bearing  directly  on  this  question,  we  have  found 
in  some  houses  that  stand  apart  from  other  structures  a  loss 
equal  to  one  third  the  extent  of  the  roof  surface.  Some  houses 
may  be  less,  but  some  more,  than  this  amount.  In  growing 
grape-vines  for  instance,  we  know  that  the  rafters  —  or  the  slop- 
ing part  of  the  house  —  is  the  principal  area  for  the  fruit-bearing 
branches  of  the  plant.  Now,  supposing  that  your  house  be  50 
feet  in  length,  15  feet  wide,  and  as  many  feet  high,  then,  by 
having  no  vines  of  any  account  growing  on  the  ends  of  the 
house,  you  lose  a  transparent  surface  equal  to  nearly  one  half 
the  extent  of  the  whole  roof.  If  it  be  asserted  that  the  perpen- 
dicularity of  the  gables  is  necessary  for  the  admission  of  hori- 
zontal light,  we  think  this  wholly  unwarranted  ;  for  experience 
has  fully  proved  that  horizontal  light,  entering  by  the  medium 
of  upright  glass,  is  powerless,  comparatively  speaking,  for  assim- 
ilating the  juices,  either  in  proper  quantity  or  quality,  for  the 
production  and  maturation  of  fine  fruit.  Many  of  the  oldest  and 
most  experienced  gardeners  prefer  hot-houses  having  no  upright 
glass  at  all  in  front,  placing  the  roof  directly  upon  a  parapet  18 
or  20  inches  in  height. 

By  way  of  remedying  the  objection  here  pointed  out,  we  have 
designed  a  house  which  combines  the  advantages  of  a  curved 
roof  with  those  of  a  plane  surface,  rendering  the  whole  of  the 
house  available  for  the  production  of  fruit.  By  this  plan  a 
greater  training  surface  is  obtained,  for  the  same  extent  of  glass 
surface,  than  by  any  other  we  know,  or  in  any  other  structure 
of  similar  dimensions.  This  we  consider  the  most  perfect  form 
of  a  hot-house  that  has  yet  been  erected. 

Fig.  19  is  intendeds  to  convey  a  clearer  notion  of  the  kind  of 
house  we  have  referred:  to»  This  house  is  100  feet  in  length, 
20  feet  in  height  at  the  back  wall,  with  a  perpendicular  rise  of 
five  feet.  The  roof  rises  in  series  of  successive  planes,  from  the 
upright  front,  and  presents  a  continuous  surface  for  training  the 
vines  to,  from  one  end  to  the  other.  Fig.  20  shows  the  ground 
plan  of  the  house,  which  may  be  made  of  any  dimensions,  as 
easily  as  any  of  the  common  forms. 


STRUCTURES   ADAPTED   TO    PARTICULAR    PURPOSES.  61 


62  STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 

A  double-roofed  house  can  be  erected  on  the  same  plan,  by 
substituting  a  row  of  columns  along  the  centre  of  the  house  for 
the  support  of  the  ridge,  in  place  of  the  back  wall ;  one  of  the 
planes  being  raised  the  necessary  height  at  each  end,  for  the 
doors,  which  must  also  be  done  in  the  single  roof,  (Fig.  19,) 
unless  the  door  enters  through  the  back  wall,  which,  in  some 
cases,  may  not  be  so  convenient  as  having  them  at  the  ends, 
though,  for  the  economizing  of  glass  surface,  we  would  prefer 
them  in  the  back  wall. 

Although  double-roofed  houses  are  generally  of  a  rectangular 
shape,  yet  they  admit  of  every  combination  of  form  without 
militating  against  the  admission  of  light  and  air.  Nevertheless, 
that  they  may  be  perfectly  adapted  to  the  end  in  view,  there  are 
rules  to  be  observed,  and  errors  to  be  guarded  against,  which  it 
is  necessary  here  to  point  out. 

If  the  house  is  above  fifteen  feet  in  width,  it  is  necessary  to 
have  a  single  or  double  row  of  columns  in  the  centre  to  support 
the  ridge  of  the  roof,  but  in  many  houses  these  columns  are 
three  times  thicker  and  heavier  than  they  ought  to  be,  even  with 
a  due  regard  to  strength  and  durability.  When  the  columns 
are  disproportionately  heavy,  the  house  has  a  dull  and  clumsy 
appearance,  and  the  effect  within  is  extremely  bad.  Indeed, 
columns  ought  to  be  dispensed  with  where  they  can  possibly  be 
spared,  consistent  with  strength  in  the  structure.  We  have 
frequently  seen  the  internal  view  of  double-roofed  houses  com- 
pletely spoiled  by  the  clumsiness  of  the  columns  supporting  the 
roof,  even  when  columns  were  altogether  unnecessary.  Cast- 
iron  columns  are  always  preferable  to  timber,  even  when  the 
structure  is  made  of  the  latter  material.  When  the  columns  or 
rafters  are  bound  together  by  braces  and  crossbars  of  slight  con- 
struction, as  of  iron  in  different  forms,  vines  and  other  climbing 
plants  may  be  trained  upon  them,  and  be  hung  in  festoons  from 
column  to  column,  or  otherwise,  as  fancy  may  dictate;  this 
gives  an  elegant  appearance,  and  is  always  pleasing  to  the  spec- 
tator. 

Another  common  error  in  the  construction  of  fruit-houses  is, 
the  heaviness  and  height  of  the  front,  something  in  the  fashion 
of  the  heavy  and  dull-looking  plant-houses  of  the  last  century. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      63 

This  results  from  a  very  general  desire  to  give  the  structure  a 
finer  effect  from  a  front  view;  but  it  must  be  regarded  as  a 
decided  sacrifice  of  utility  and  adaptation  to  purpose.  Making 
the  front  of  graperies  from  eight  to  ten  or  twelve  feet  high, 
is  not  less  objectionable  than  to  make  the  roof  on  a  level  with 
the  plane  of  the  horizon.  The  sides  of  a  hot-house  should  never 
be  more  than  four  or  five  feet  in  height.  This  gives  the  struc- 
ture a  more  characteristic  appearance,  and  is  certainly  much 
more  fitted  for  the  purpose  in  view,  than  upright  sashes,  which 
make  the  roof  appear  to  the  eye  only  a  fraction  of  its  real  extent, 
whether  viewed  from  the  interior  or  the  exterior  of  the  structure, 
apart  from  the  consideration,  that  the  upright  part  of  the  house 
neither  produces  nor  ripens  the  berries  of  grapes  so  well  as  the 
sloping  part  of  the  transparent  surface.  All  structures  of  glass, 
for  horticultural  purposes,  should  have  a  parapet  wall,  from  12 
to  20  inches  in  height,  on  which  to  rest  the  frame-work  of  the 
fabric ;  then  about  four  feet  of  upright  glass.  This  modification 
gives  the  house,  whether  of  large  or  small  dimensions,  a  neat 
and  characteristic  appearance.  A  span-roofed  house,  24  feet 
wide  and  16  feet  high,  with  a  five-feet  front,  makes  a  well- 
proportioned  house,  and  gives  about  16  feet  of  a  run  for  the 
vines  under  the  rafters,  —  the  slope  of  the  roof  being  upon  an 
angle  of  45°,  which,  as  we  have  already  said,  is  the  best  pitch 
for  a  hot-house  roof  for  general  purposes. 

Until  these  few  years,  the  forms  of  hot-houses  were  generally 
plain,  flat,  right-lined  buildings,  differing  in  no  respect  from  one 
another  than  in  their  size  and  relative  degrees  of  clumsiness. 
Lately,  however,  a  great  improvement  has  taken  place  in  the 
form  and  construction  of  this  class  of  buildings.  Single-roofed 
houses  are  fast  dwindling  into  desuetude,  and  right-lined  houses 
are  giving  way  to  the  more  light  and  elegant  curvilinear  roofs. 
This  is  an  important  step  in  the  right  way;  and  we  regard 
those  who,  laying  aside  their  prejudices  in  favor  of  right-lined 
houses,  adopt  the  curvilinear  shape,  as  conferring  a  benefit  on 
exotic  horticulture  as  acceptable  to  those  interested  in  the  pro- 
fession as  it  is  creditable  to  themselves. 

Regarding  curved  houses,  Loudon  says,  —  "On  making  a 
few  trials,  to  ascertain  the  variety  of  forms  which  might  be 


64  STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 

given  to  hot-houses  by  taking  different  segments  of  a  sphere, 
I,  however,  soon  became  fully  satisfied  that  forcing-houses,  of 
excellent  forms  for  almost  every  purpose,  and  of  any  convenient 
extent,  might  be  constructed  without  deviating  from  the  spheri- 
cal form ;  and  I  am  now  perfectly  confident  that  such  houses 
will  be  erected  and  kept  in  repairs  at  less  expense,  will  possess 
the  important  advantage  of  admitting  much  more  light,  and  will 
be  found  much  more  durable,  than  such  as  are  constructed 
according  to  the  methods  and  forms  which  have  hitherto  been 
recommended." 

Fig.  21  is  a  representation  of  what  is  called  the  zig-zag,  or 
ridge-and-furrow  roof,  which  has  not,  as  far  as  we  know,  been 
very  extensively  adopted.  There  are  several  places  in  Eng- 
land where  this  method  of  roofing  has  been  adopted,  but  prin- 
cipally as  an  experiment,  or  merely  as  the  fancy  of  the  erector. 
The  advantage  of  this  mode  ,of  roofing  is,  that  the  rays  of  the 
sun  are  presented  more  perpendicularly  to  the  glass  in  the 
morning  and  afternoon,  when  they  are  weakest,  and  more 
obliquely  to  the  glass  at  noon,  when  they  are  strongest.  We 
doubt,  however,  —  though  the  arguments  we  have  heard  urged 
in  favor  of  this  kind  of  houses  be  indisputable,  —  whether  the 
additional  expense  required  in  their  construction  will  be  coun- 
terbalanced by  the  advantages  gained.  There  is  no  doubt  the 
expense  of  their  erection  militates  very  much  against  them ;  and, 
if  they  could  be  erected  as  cheap  as  plane  roofs,  they  are  decid- 
edly superior  to  them  for  graperies,  as  the  vine  can  be  trained 
up  the  middle  of  the  ridge,  and,  consequently,  though  suffi- 
ciently near  the  glass,  the  intense  rays  of  the  sun  will  be  less 
injurious  than  under  a  plane  roof. 

The  ridge-and-furrow  roof  may  be  carried  out  either  on  com- 
mon plane-roofed  houses,  or  on  the  curvilinear  principle,  though 
doubtless  the  latter  is  more  difficult  of  construction,  and,  of 
course,  more  expensive ;  but  we  have  no  doubt,  if  the  principle 
of  constructing  horticultural  structures  were  fully  understood  by 
competent  manufacturers,  who  had  directed  their  attention  to 
the  details  of  the  structures,  that  this,  or,  in  fact,  any  other 
form  of  structure,  could  be  made  as  cheap  as  the  houses  now  in 
common  use. 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES.  65 


Fig.  21. 


66       STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

The  ridge-and-furrow  roof  may  be  formed  by  placing  the 
rafters  as  in  making  a  common  roof,  say  four  feet  apart;  then 
placing  the  ridge-bars  in  such  a  manner  that,  contiguous  to  each 
other,  they  will  form  an  angle  of  45°  with  the  furrow-bar,  or 
rafter.  Or  the  angle  included  within  the  ridge-bar  may  be 
formed  to  suit  the  climate  of  the  neighborhood,  —  bearing  in 
mind  the  principles  already  laid  down  regarding  the  effects  of 
intense  sunshine  upon  flat  roofs. 

The  sides  of  the  ridge  may  be  glazed  of  small  panes,  as  in 
common  sashes,  or  may  be  made  of  single  panes,  as  in  the  finest 
houses  now  erected ;  but,  whichever  method  is  adopted,  the 
rafters  should  terminate  in  one  horizontal  line  on  the  top  of  the 
parapet :  this  is  also  desirable  at  the  back  wall.  Some  apparent 
difficulty  is  thus  occasioned  in  the  lower  part  of  the  roof;  but 
this  difficulty  is  only  apparent,  especially  if  the  front  of  the 
ridge  be  made  to  slope  on  the  same  angle  as  the  side.  Only 
the  smaller  and  triangular  pieces  of  glass  can  be  used.  It 
becomes,  in  fact,  more  economical,  as  the  smaller  pieces  of  glass 
may  be  all  used  up,  which  would,  otherwise,  be  thrown  away. 

The  ridge-and-furrow  roofs  are  especially  advantageous  in 
countries  liable  to  heavy  falls  of  snow  or  rain,  and  in  large 
houses  which  are  parallelograms  in  plan.  Almost  any  wreight 
of  snow  may  be  carried  by  such  roofs,  especially  where  the  fur- 
row is  small,  as  the  pressure  will  then  be  chiefly  on  the  bars 
and  rafters,  and  not  on  the  glass.  As  to  hail,  which  is  some- 
times very  heavy  in  this  country,  breaking  the  glass  in  flat-roofed 
houses,  it  will  always  meet  the  glass  of  a  ridge-and-furrow  house 
at  an  angle  which  will  prevent  breakage. 

The  advantages  of  these  ridge-and-furrow  roofs,  as  we  have 
already  stated,  —  their  presenting  the  surface  of  the  glass  at  an 
oblique  angle  to  the  noon-day  sun,  while  the  morning  and  even- 
ing sun  is  admitted  almost  perpendicular  to  the  surface  on 
which  it  falls,  —  ought  not  to  be  altogether  overlooked  in  this 
country;  and  we  think  that  a  great  deal  might  be  done  with 
houses  of  this  kind, — probably  upon  an  improved  plan, — where- 
by the  effect  of  the  intense  sunshine  of  mid-summer  might  be,  in 
some  measure,  deprived  of  its  meridian  force  upon  glass-houses. 
Whatever  may  be  thought  of  the  plan  here  given,  the  principle 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES.  67 

upon  which  it  is  made  is  undoubtedly  good ;  —  a  principle  which 
may  easily  be  illustrated  by  placing  a  few  common  frame- 
sashes  in  the  positions  of  the  supposed  ridge-and-furrow  roof, 
placing  some  tender-foliaged  plants  beneath  them,  and  then 
comparing  the  results,  under  intense  sunshine,  with  the  effects 
produced  under  a  common  sash,  whose  surface  is  perpendicular 
to  the  noon-day  sun. 

Whatever  might  be  said  in  favor  of  cold  vineries,  they  are, 
nevertheless,  subject  to  casualties  which  are  necessarily  una- 
voidable. This  is  more  especially  the  case  in  the  Northern 
States ;  and  even  as  far  south  as  the  latitude  from  which  we 
now  write,  (39°  45',)  they  are  liable  to  the  same  mishaps.  All 
houses  for  the  production  of  foreign  grapes  should  have  some 
means  or  other  of  commanding  a  little  artificial  heat  when  it  is 
found  absolutely  necessary.  This  does  not  amount  to  saying 
that  good  crops  have  not  and  may  not  be  grown  in  cold-houses, 
without  any  means  of  raising  the  temperature  in  cold  nights ; 
yet  it  cannot  be  denied  that  good  crops  have  been  sacrificed  for 
the  want  of  a  slight  fire  in  frosty  nights.  This  is  particularly 
the  case  in  nectarine  and  peach  houses,  where  we  have  seen  the 
crop  completely  destroyed  in  a  single  night. 

Experience  has  fully  shown  that  the  culture  of  exotic  fruits  is 
a  precarious  business,  without  some  readily  available  means  of 
averting  those  evils  which  are  neither  modified  nor  averted  by 
any  peculiar  mode  of  construction,  or  any  angle  that  can  be 
given  to  the  roof.  This  circumstance  is  worthy  of  particular 
attention,  as  many  persons  who  design  hot-houses  lay  particular 
stress  on  certain  trifling  details  in  the  structure,  which,  in  a 
practical  point  of  view,  are  unworthy  of  the  least  notice. 

We  have  lately  had  some  conversations  with  men  thoroughly 
skilled  in  the  science,  as  well  as  the  practice,  of  vine-growing 
and  the  details  of  hot-house  management,  and  have  particularly 
noted  the  diversity  of  opinion  regarding  the  upright  portion  of 
the  front  of  the  house.  Some  are  of  opinion  that  hot-houses  for 
the  culture  of  fruit  should  have  no  parapet-wall,  but  that  the 
sashes  should  rest  on  a  water-plate  level,  or  nearly  level,  with 
the  ground,  giving,  as  a  reason,  the  fact  that  the  parapet  pre- 
vents the  sun  and  light  from  getting  to  the  inside  border,  and  to 


68  STRUCTURES    ADAPTED   TO    PARTICULAR    PURPOSES. 

the  stems  of  vines.  Now,  with  regard  to  small  winter  forcing- 
houses,  this  may  be  of  some  effect ;  but  in  cold  summer-houses, 
i.  e.,  houses  intended  for  growing  peaches,  grapes,  etc.,  without 
fire  heat,  this  is  of  no  importance,  as  the  meridian  altitude  of 
the  sun  during  summer  renders  the  wall  rather  beneficial  than 
injurious,  by  shading  the  border  during  the  heat  of  the  day. 
Hence,  it  is  evident  that  the  construction  of  the  house  for 
grape-growing,  etc.,  should  be  regulated  according  to  the  locality, 
as  well  as  the  period  of  the  year  at  which  it  is  required  to  ripen 
the  fruit. 

Many  have  a  serious  objection  to  upright  fronts,  whether  of 
glass  or  other  material,  from  the  undeniable  fact  that  fruit  is 
seldom  produced  below  the  angle  of  the  rafter ;  and  if  it  is,  it 
never  ripens  so  well  as  that  grown  under  the  perpendicular 
light,  nor  is  so  well-flavored.  Upright  glass,  however,  adds  so 
much  to  the  appearance  of  this  kind  of  building,  that  it  can 
hardly  be  dispensed  with,  even  at  the  sacrifice  of  a  little  fruit ; 
but  the  latitude  here  allowed  must  be  kept  within  certain  limits, 
otherwise  the  effect  produced  is  worse  than  if  the  house  had  no 
parapet  at  all. 

The  parapet  wall  of  a  peach-house  or  grapery  should  never 
be  more  than  twenty  inches  or  two  feet  high ;  the  perpendicular 
sash  above  it,  three  feet  more,  making  the  upright  front  five  feet 
in  all.  This  is,  we  think,  a  proper  height  for  structures  of  the 
kind  here  referred  to ;  and  this  will  be  found  to  give  the  struc- 
ture, whatever  its  longitudinal  dimensions,  better  proportions, 
and  a  more  handsome  appearance,  than  if  these  dimensions  be 
either  diminished  or  increased. 

In  many  private  establishments  it  is  much  more  convenient 
to  have  one,  two,  or  more  houses,  than  to  have  one  single 
house  perhaps  equal  to  the  length  of  the  whole.  We  happen 
to  know  several  persons  who  prefer  erecting  houses  for  grapes 
and  peaches  in  this  way ;  and,  indeed,  it  has  many  advantages 
over  building  a  large  house,  especially  for  private  establish- 
ments of  moderate  extent,  where  the  whole  produce  is  consumed 
by  the  family,  because  one  house  may  be  advanced  a  month  or 
two  before  the  succeeding  one,  while  the  third  may  be  protracted 
as  late  as  possible,  so  that  the  fruit  season  will  be  much  longei 


STRUCTURES    ADAPTED   TO    PARTICULAR    PURPOSES.  69 


== 


70      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

than  if  the  structure  was  composed  of  a  single  house  of  the  size 
of  the  three. 

In  building  a  range  of  hot-houses  on  these  principles,  say  one 
hundred  feet  long,  we  would  arrange  them  in  the  order  rep- 
resented in  the  opposite  cut,  Fig.  22,  showing  three  houses 
united  into  a  neat  and  compact  range.  The  centre  division, 
which  is  more  elevated  than  the  others,  may  be  used  as  an 
orangery,  or  camellia  house ;  or  for  growing  figs,  planting  the 
trees  in  the  centre  bed  and  growing  them  as  common  dwarfs, 
which  is  the  best  way  of  growing  figs,  their  strong  and  uncom- 
pliable  branches  being  unsuited  for  training  on  the  common 
trellises  of  a  vinery,  neither  do  they  fruit  so  well  as  when 
allowed  to  grow  like  a  dwarf  pear-tree. 

These  dimensions  are  also  advantageous  on  account  of  the 
trees  that  are  to  be  grown  in  them,  as  different  kinds  of  trees 
require  different  kinds  of  treatment,  as  well  as  different  degrees 
of  heat,  air,  and  moisture.  Each  kind  of  tree  can  have  the 
treatment  which  is  most  conducive  to  health  and  fruitfulness, 
without  infringing  on  the  peculiar  conditions  required  by  the 
others. 

Where  a  large  quantity  of  fruit  is  required,  the  houses  for  its 
production  must,  of  course,  be  upon  a  larger  scale.  We  men- 
tion this,  as  very  absurd  ideas  are  frequently  entertained  by 
individuals  regarding  the  producing  capacity  of  vines,  etc.,  in 
houses,  being  ignorant  of  the  quantity  that  healthy  trees  can 
bear  without  inflicting  a  permanent  injury. 

If  it  be  desired,  the  centre  compartment  of  this  range  may  be 
converted  into  a  green-house,  by  placing  a  stage  along  the  mid- 
dle of  the  house,  and  a  front  shelf  two  feet,  wide  along  the  front 
nearly  level  with  the  building  of  the  parapet  wall,  leaving  a 
sufficient  space  between  the  shelf  and  the  stage  for  a  pathway. 
The  plan  of  placing  the  green-house  in  the  centre,  between 
the  fruit-houses,  is  very  common.  The  plans  of  modern  archi- 
tects are  somewhat  different  from  those  of  the  last  century, 
in  which  we  generally  find  the  green-house  a  part  of  the  cul- 
inary department,  either  in  the  middle,  or  in  a  corner  of  the 
kitchen  garden.  In  fact,  little  can  be  said  in  favor  of  placing 
the  green-house  or  plant-stove  among  the  fruit-houses,  except 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      71 

in  small  places  where  the  limits  of  the  ground  do  not  admit  of 
a  select  position,  or  where  it  may  be  desirable  to  place  the  whole 
of  the  glass  structures  together,  either  for  economy,  conven- 
ience, or  effect. 

When  a  grapery  having  some  pretensions  to  architectural 
display  is  desired,  either  to  correspond  with  buildings  already 
on  the  place,  or  to  form  a  connection  between  some  portion  of 
the  mansion  and  another,  then  the  structure  may  possess  a 
heavier  and  more  artistic  character.  This  may  be  accomplished 
without  in  the  slightest  degree  infringing  on  the  principle  of 
adaptability.  For  instance,  there  may  be  a  recess,  with  the 
proper  aspect,  in  some  part  of  the  mansion,  which  the  proprietor 
may  wish  to  fill  up  with  a  house  productive  of  profit  as  well  as 
pleasure ;  and  for  this  purpose,  he  chooses  a  grapery,  and  wishes 
a  suitable  house  for  the  purpose,  without  destroying  the  general 
harmony  of  his  mansion.  Or,  perhaps,  his  premises  may  be 
very  limited  in  extent,  and  he  wishes  a  fruit-house  nearly  of 
the  same  order  as  his  Tuscan  or  Italian  villa ;  in  which  case,  a 
house  with  a  somewhat  massive  parapet  and  blocking-course,  as 
in  Fig.  23,  would  be  more  in  unison  with  his  taste,  as  well  as 
with  the  rest  of  the  premises. 

This  house,  it  will  be  observed,  has  rectangular  ventilators  in 
the  front  wall,  which  give  the  house  a  more  architectural 
appearance ;  the  back  wall  is  also  surmounted  by  an  ornamental 
blocking-course,  with  ventilators  for  the  admission  of  air  through 
the  back  wall.  [See  Ventilation.] 

We  do  not,  by  any  means,  justify  the  method  of  placing 
fruit-houses  immediately  contiguous  to  the  dwelling,  yet  such 
is  the  taste  of  many.  And  as  there  is  no  valid  reason  why 
persons  may  not  carry  out  their  particular  fancies  with  their  own 
property,  we  have  made  the  foregoing  remarks  for  their  benefit. 

We  do  not  give  the  above  cut  as  a  model  house  for  an  archi- 
tectural vinery,  —  of  course,  its  ornamental  character  may  be 
increased,  according  to  the  money  that  is  to  be  devoted  to  its 
erection ;  but  with  regard  to  the  principles  of  its  design,  unless 
the  polyprosopic  roof  be  adopted,  which  is  considered  by  some 
more  architectural  in  its  appearance  than  curvilinear  roofs, 
when  conjoined  to  the  square  forms  of  Dwelling-houses. 
7 


STRUCTURES    ADAPTED    TO    PARTICULAR    PURPOSES. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      73 

3.  Green-houses,  Conservatories,  fyc.  —  The  principal  dis- 
tinction between  a  green-house  and  conservatory  is,  that  in  the 
former,  the  plants  are  exhibited  upon  shelves  and  stages,  while, 
in  the  latter,  the  plants  are  generally  planted  out  in  a  bed  in  the 
middle  of  the  house  prepared  for  their  reception.  In  many 
instances,  however,  there  is  no  other  distinction  than  in  the 
name ;  as  these  structures  are  sometimes  so  arranged  that  the 
middle  portion  is  appropriated  to  the  growth  of  larger  plants 
planted  out,  while  the  sides  are  surrounded  with  shelves  for  the 
reception  of  plants  in  pots,  as  in  a  common  green-house.  And 
to  this  arrangement  there  can  be  no  special  objection,  especially 
where  the  structure  is  of  small  dimensions,  which  admits  of  the 
sides  being  shelved  for  plants  in  pots,  without  destroying  the 
character  of  the  house,  or  the  plants,  by  their  distance  from  the 
glass.  We  have  seen  a  few  instances,  a  very  few,  where  the 
two  characters  were  amalgamated  together,  forming  a  most 
interesting  conjunction;  but,  unless  the  specimens  exhibited  be 
very  large  and  well-grown,  their  effect,  when  situated  upon  the 
centre  bed  of  a  common-sized  house,  surrounded  with  shelves, 
is  meagre  and  defective  in  the  last  degree. 

Properly  speaking,  a  green-house  is  not  a  receptacle  for  large 
plants,  and  hence  it  should  have  adequate  means  within  it  for 
standing  the  plants  within  a  proper  distance  from  the  glass. 
This  is  absolutely  necessary  with  regard  to  those  classes  of  flow- 
ering plants  that  are  fitted  to  adorn  it,  both  in  winter  and  sum- 
mer. Some  are  of  opinion  that  green-houses  are  of  no  further 
service  than  merely  to  store  away  a  miscellaneous  assortment 
of  rubbish  during  the  months  of  winter,  for  the  obvious  purpose 
of  preserving  them  until  the  next  summer,  that  they  may  turn 
them  out  under  trees,  or  in  out-of-the-way  corners,  to  keep  them 
from  being  burnt  up  by  the  hot  summer  sun ;  and,  as  a  matter 
of  course  and  of  custom,  the  green-house  is  converted  into  a 
lumber-room,  or  something  else.  And  there  it  stands  !  what  is, 
or  ought  to  be,  the  chief  ornament  of  the  garden,  deprived  of  its 
character,  for  want  of  taste,  and  divested  of  its  interest,  for  lack 
of  skill!  Visitors  say,  "Let  us  have  a  look  at  the  green- 
house." "  No,"  replies  the  gardener,  apologetically,  "  it 's  not 


74      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

worth  your  while  going  in,  for  there  is  nothing  there  to  see ! " 
A  humiliating  acknowledgment,  but  full  of  truth. 

It  is  foreign  to  our  purpose  to  enter  upon  the  present  condi- 
tion of  green-house  gardening,  and  the  mariner  in  which  these 
structures  are  managed  by  gardeners.  Our  present  object  is  to 
treat  of  their  construction,  and  of  the  means  of  adapting  them 
the  most  easily  to  the  culture  of  flowering  plants,  either  during 
winter  or  summer. 

It  is  a  well  known  fact,  that  plants  that  are  grown  in  what 
are  called  lean-to  green-houses,  have  exactly  the  character  of 
the  house  in  which  they  are  grown,  i.  e.,  they  are  one-sided ; 
nor  is  it  possible,  without  a  vast  amount  of  labor  and  attention 
on  the  part  of  the  gardener,  to  grow  them  otherwise.  In  this 
respect  the  cultivator  does  not  imitate  nature,  but  rather  the 
monstrosities  of  nature.  Trees  and  shrubs  only  grow  one-sided 
when  their  position  precludes  the  access  of  light  and  air  around 
them;  but  they  grow  naturally  into  a  compact  bush,  which  is 
universally  allowed  to  be  the  most  beautiful  form  that  plants 
can  assume. 

Even  a  handful  of  cut  flowers  have  their  beauty,  and  are 
generally  admired,  but  when  seen  upon  the  living  plant, 
whatever  shape  or  form  the  latter  may  possess,  how  much 
greater  their  charms !  If,  therefore,  we  add  to  these  natural 
beauties  the  additional  charm  of  a  positively  beautiful  form, 
surely  it  will  double  their  claim  to  our  admiration.  And  we 
may  here  add  the  gratifying  fact,  that  this  claim  is  now  gener- 
ally recognized  by  all  who  can  appreciate  the  superior  beauty 
©f  well-grown  plants. 

The  principles  upon  which  plant  structures  ought  to  be  built, 
are  somewhat  different  from  those  which  regulate  the  erection 
of  forcing-houses,  culinary  houses,  &c.,  and  as  their  purposes 
are  different,  their  shapes  and  forms  are  generally  also  different. 
Plant-houses  admit  of  a  greater  variety  of  shape  and  design 
than  any  of  the  kinds  previously  mentioned,  and  as  they  are 
generally  erected  in  private  grounds,  for  ornament  and  display, 
they  should  have  a  more  artistic  character  than  the  others. 

The  size  of  the  green-house  may  vary  according  to  the  extent 
of  the  collection  to  be  cultivated,  but  it  should  always  have  a 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      75 

length  proportionate  to  its  height  and  width.  There  is  a  great 
inconvenience  in  having  the  green-house  very  capacious,  and 
where  it  is  desirable  to  have  a  large  collection  of  plants,  it  is 
best  to  have  a  conservatory  for  the  growth  of  the  larger  speci- 
mens, or  a  stove  for  the  palmaceous  families  of  plants.  We 
shall,  however,  allude  to  what  is  properly  termed  the  green- 
house. 

A  first-rate  green-house  should  be  completely  transparent  on 
all  sides ;  lean-to  houses  are  decidedly  objectionable,  for  the 
reasons  already  given.  Houses  that  are  only  glazed  in  front, 
and  have  glass  roofs,  but  otherwise  opaque,  are  also  objection- 
able, as  plants  can  never  be  made  to  grow  handsome.  They 
become  weakly  and  distorted  by  continually  stretching  towards 
the  light,  neither  do  they  enjoy  the  genial  rays  of  the  morning 
and  evening  sun,  and  only  perhaps  for  a  few  hours  during  mid- 
day. If  such  houses  be  large  and  lofty,  they  are  still  more  un- 
manageable, as  no  culture  can  keep  the  plants  symmetrical  and 
of  good  appearance. 

A  green-house  should  stand  quite  detached  from  all  other 
buildings,  and  may  be  of  any  form  the  fancy  may  dictate,  or  the 
position  suggest.  It  may  be  circular,  oval,  hexagonal,  octagonal, 
or  a  parallelogram,  with  circular  or  curved  ends.  The  house, 
to  be  proportionate,  should  be  about  fifty  feet  in  length  by  twenty 
in  width,  and  fourteen  feet  high,  above  the  level  of  its  floor;  if 
more  effect  be  required  from  the  external  view,  its  parapets  may 
be  raised,  to  give  the  house  a  loftier  appearance.  The  parapet 
should  be  not  more  than  two  feet  high  all  round,  the  upright 
glass  about  two  and  a  half  or  three  feet  more,  including  base, 
plate,  and  sash  bars.  The  house  should  be  surrounded  by  a 
shelf,  two  feet  wide,  level  with  .the  top  of  the  parapet  wall. 
This  shelf  is  of  great  importance  to  a  gardener,  and  is  gener- 
ally the  best  place  for  the  finer  kinds  of  plants ;  being  sur- 
rounded on  all  sides  with  light,  and  being  near  the  glass,  they 
grow  bushy  and  dwarf  in  habit,  in  which  state  they  are  most 
pleasing  and  attractive.  Next  to  this  shelf  comes  the  pathway, 
three  feet  wide  at  least,  (having  just  enough  room  between  the 
roof  for  the  tallest  individual  to  clear  the  glass  and  rafters;) 
then  the  stage,  or  centre-tables,  of  stone  or  timber,  and  arranged 
7* 


76 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 


according  to  the  size  of  the  plants  to  be  grown.  The  following 
end  section  will  illustrate  what  we  here  refer  to.  It  is  somewhat 
enlarged,  for  the  purpose  of  showing  the  arrangements  of  the 
interior.  The  cut  which  follows  (Fig.  25)  is  a  perspective  view 
of  the  same  house,  taken  at  a  considerable  distance  from  it,  for 
the  purpose  of  showing  the  effect  of  this  plain  structure  in  a 
pleasure-ground.  If  desired,  it  may  be  made  to  assume  some- 
thing of  the  character  of  a  conservatory,  by  introducing  a  ground 
bed  in  the  centre,  instead  of  the  shelves  or  tables.  The  fire- 
place and  heating  apparatus  may  be  placed  at  one  end,  and 
under  ground,  so  as  to  be  out  of  sight,  or  may  be  formed  in  a 
sunk  shed,  and  blinded  with  shrubbery.  The  flues,  or  pipes,  for 
warming  the  house,  must  be  carried  round,  beneath  the  side 
shelves,  dipping  below  the  level  of  the  floor  at  the  doors,  and 
returning  by  the  opposite  side  of  the  house  to  the  furnace.  The 
cost  of  each  a  structure  will  very  much  depend  upon  the  quality 
of  the  workmanship,  and  the  material  used  in  the  construction ; 
but  we  think  a  very  good  house  may  be  erected,  according  to  the 
foregoing  plan,  for  about  ten  dollars  per  foot  in  length,  or  about 
five  hundred  dollars  for  a  house  50  feet  long  by  20  feet  in  width. 

Fig.  24. 


Such  a  green-house,  though  plain  and  inexpensive  in  its 
character,  may,  nevertheless,  be  made  to  harmonize  well  with 
flower-garden  scenery,  and  is  far  superior  to  the  clumsy,  shed- 
like  erections  frequently  seen  stuck  into  corners  of  buildings 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 


77 


and  dwelling-houses,  without  reference  to  the  position  of  the 
structure,  or  the  purpose  for  which  it  was  built. 

Fig.  25  shows  the  appearance  of  the  house,  on  the  proportions 
which  are  given  in  the  above  plan,  (Fig.  24,)  which,  in  our 
opinion,  admits  of  more  room  for  plants  than  any  other  form 
that  can  be  built  at  the  same  cost ;  for,  although  we  might  adopt 
a  semi-circular  form  for  the  end  toward  the  most  prominent 
point  of  view,  it  must  be  remembered  that  this  would  add  con- 
siderably to  its  cost.  Our  object  here  is  to  give  the  sketch  of 
the  best  and  cheapest  kind  of  house  that  can  be  erected  for  plant- 
growing,  and  such  is  the  one  here  given. 

This  house  may  be  placed  in  any  situation,  as  regards  aspect. 
It  may  be  attached  at  one  end  to  any  other  building,  without 
much  injury  to  its  efficiency  as  a  plant-house ;  and  where  it  is 
found  absolutely  necessary  to  attach  green-houses  to  the  walls 
of  other  buildings,  they  should,  by  all  means,  be  constructed 
after  the  plan  here  given,  or  under  some  architectural  modifica- 
tion of  it,  avoiding,  if  possible,  that  old,  and  now  almost  obsolete, 

Fig.  25. 


system,  of  laying  the  roof  up  to  the  wall,  as  in  a  common 
grapery,  or  of  making  the  front  of  heavy  pilasters  and  massive 
wood-work,  like  the  orange-houses  of  the  middle  ages.  The 
method  of  construction  here  described  is  that  in  which  the 
plants  enjoy  the  largest  share  of  light ;  and  this  house  is  the 
easiest  managed  —  with  respect  to  air  and  heat  in  winter,  and 
moisture  and  shade  in  summer — of  all  other  methods  which 
have  come  under  our  experience. 


7S      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      79 

In  some  establishments  it  may  be  requisite  to  have  a  range 
of  plant-houses,  or  one  house  divided  into  compartments,  for 
the  different  kinds  of  plants ;  thus  the  structure  may  be  of  a 
highly  ornamental  character,  as  in  Fig.  26,  one  end  consisting 
of  a  common  green-house,  for  geraniums  and  soft-wooded  plants, 
and  the  other  may  be  either  a  heathery,  an  orchidaceous,  or  an 
exotic  stove,  for  promiscuous  plants ;  the  centre,  being  larger  and 
more  capacious  than  the  ends,  may  be  an  orangery,  or  a  palm- 
house. 

This  forms  an  elegant  range  of  botanic  hot-houses,  and  being 
of  glass  all  round,  should  stand  in  the  middle  of  a  large  pleasure- 
ground,  or  shrubbery.  The  smoke  of  the  furnaces,  being  con- 
ducted into  a  subterraneous  canal,  is  carried  to  a  distance,  and 
emitted  by  means  of  a  shaft  having  the  appearance  of  an  orna- 
mental column,  as  in  the  Botanic  Gardens  of  Edinburgh  and 
Kew. 

By  having  the  plant-stove  in  the  middle  of  the  other  houses, 
a  considerable  advantage  is  gained  by  the  protection  afforded  in 
winter,  when  the  structure  requires  to  be  kept  at  a  high  temper- 
ature by  artificial  means ;  and  as  both  of  the  adjoining  houses 
will  also  be  warmed  in  severe  weather,  the  centre  one,  though 
larger,  will  be  maintained  at  the  required  temperature  with  a 
heating  apparatus  no  larger  than  the  others. 

From  the  curved  disposition  of  the  centre  house,  this  range 
has  a  peculiarly  pleasing  effect,  when  viewed  from  a  horizontal 
point  of  view  somewhat  distant.  The  proportions  of  this  struc- 
ture are  excellent ;  and  it  would,  undoubtedly,  form  a  splendid 
ornament  in  the  grounds  of  a  gentleman's  country-seat. 

One  of  the  leading  errors  in  the  erection  of  large  plant-houses, 
is  in  the  unreasonable  height  to  which  their  roofs  are  carried,  and 
which  in  the  case  of  palm-houses  may  be  defended  as  necessary ; 
but  in  the  case  of  conservatories,  there  is  no  tenable  justification 
of  such  a  course,  except  the  house  is  intended  to  be  the  object 
of  admiration,  instead  of  the  plants  that  are  grown  in  it ;  and 
if  fitness  for  the  end  in  view  be  expressive  of  beauty,  then,  after 
all,  these  architectural  temples  must  decidedly  fail  in  producing 
that  effect  upon  the  mind,  that  the  plain  finished,  but  fitly  and 
efficiently  designed  structure  never  fails  to  produce.  But  the 


80  STRUCTURES    ADAPTED    TO    PARTICULAR   PURPOSES. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      81 

beauty,  even  of  the  plainest  kind  of  structures,  may  be  easily 
heightened  and  increased  by  an  ornamental  moulding  of  wood 
along  the  ridge  of  the  roof,  if  a  span,  or  on  the  end  rafters  and 
front  plate,  as  in  Figs.  26  and  27,  which  will  deprive  the  house 
of  none  of  its  lightness,  and  will  give  it  a  neater  and  more  ele- 
gant appearance. 

Plants  placed  at  a  distance,  either  under  water  or  under  glass, 
arc  as  much  influenced  in  their  development  by  the  light  as  by 
the  heat.  When  plants  are  a  great  distance  from  the  roof,  they 
are,  of  course,  in  a  colder  and  denser  medium  at  the  surface  of 
the  soil  than  at  the  top  of  the  house,  and  there  cannot  be  a 
doubt  that  this  difference  in  the  density  and  temperature  of  the 
atmosphere  has  much  to  do  with  the  struggle  and  effort  which 
every  plant  makes  to  rise  upward,  and  to  elevate  its  assimilating 
organs  into  the  warmer  and  most  humid  regions  of  the  house. 
It  will  also  be  found  that  the  difference  betwixt  the  higher  and 
lower  strata  of  air  in  hot-houses,  is  more  immediately  the  cause 
of  plants  drawing,  and  becoming  weak,  than  anything  that  re- 
sults from  a  feeble  constitution,  or  from  a  deficiency  of  atmos- 
pheric air. 

Notwithstanding  the  practical  illustrations  of  this  prevailing 
error  in  plant-houses,  there  seems  to  have  been  very  little  done 
to  counteract  this  fault  in  lofty  houses.  The  large  conservatory 
in  the  Regent's  Park,  Botanic  Garden,  is  the  only  structure  of 
great  size  where  this  circumstance  has  had  sufficient  weight  to 
induce  the  erectors  to  provide  against  it,  in  the  general  design 
and  construction  of  the  building.  This  admirable  plant-house 
stands  as  a  striking  illustration  of  what  can  be  done  on  a  grand 
scale,  without  rendering  fitness  for  the  end  in  view  subservient 
to  architectural  display,  and  yet,  without  depriving  the  structure 
of  that  dignity  and  effect  which  fine  conservatories  always  convey 
to  the  cultivated  mind.  This  conservatory,  we  believe,'  is  the 
result  of  well  digested  practical  and  scientific  knowledge,  and 
we  doubt  if  there  be  any  other  such  erection  in  England,  where 
the  effect  of  this  rare  combination  is  so  strikingly  displayed  on 
a  scale  so  magnificent;  and  the  result  of  this  combination  has 
indeed  been  clearly  manifested,  in  the  formation  and  subsequent 
management  of  this  beautiful  garden. 


82      STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES. 

As  the  influence  of  the  upper  and  lower  strata  of  air,  in  large 
houses,  will  be  discussed  in  a  subsequent  portion  of  this  work, 
devoted  to  that  subject,  we  will  not  enlarge  further  upon  it  at 
present,  more  than  to  observe,  that  lofty-domed,  or  curvilinear 
roofs,  as  that  lately  erected  at  Kew,  are  more  difficult  to  manage, 
both  in  winter  and  summer,  than  low-roofed  houses,  whether 
curved  or  straight,  and  that  the  impossibility  of  rendering  these 
houses  in  any  way  workable,  has  induced,  in  some  instances, 
their  almost  entire  abandonment  on  the  part  of  the  proprietors, 
owing  solely  to  the  intense  heat  of  the  superior  regions  of  the 
house. 

The  most  experienced  and  enlightened  men  have  satisfied 
themselves,  that  structures  in  which  the  atmosphere  has  to  be 
kept  at  a  higher  temperature  than  the  external  atmosphere,  and 
in  which  plants  have  to  be  grown,  should  be  kept  at  the  very 
lowest  elevation  which  the  use  and  purpose  will  admit,  so  that 
the  temperature  of  the  air,  at  the  level  of  the  floor,  and  among 
the  roots  and  lower  portions  of  the  plants,  may  be  as  little  dif- 
ferent as  possible  from  what  it  is  in  the  higher  regions  of  the 
house;  by  regarding  which,  the  house  will  be  much  easier  kept 
during  summer,  with  respect  to  air  and  moisture,  and,  during 
winter,  with  respect  to  a  more  equal  diffusion  of  heat. 

In  the  comparatively  still  atmosphere  of  a  hot-house,  when  all 
is  closely  shut  up  in  a  cold  winter's  night,  the  difference  betwixt 
the  temperature  of  the  atmosphere  at  the  surface  of  the  floor 
and  the  highest  part  of  the  roof  will  generally  be  in  the  ratio 
of  one  degree  to  every  two  feet  of  elevation ;  thus,  in  a  house 
20  feet  high  there  will  be  a  difference  of  10°,  and  in  a  house  60 
feet  high  the  same  rule  gives  a  difference  of  no  less  than  30  de- 
grees. This  ratio,  however,  is  riot  absolutely  correct,  as  we 
have  proved  by  experiment,  in  houses  of  various  sizes,  which 
give,  under  certain  circumstances,  a  greater  difference  of  tem- 
perature than  here  stated,  as  will  be  shown  when  we  come  to 
treat  on  this  branch  of  horticultural  science.* 

We  have  already  said  enough  on  this  point,  here,  to  show  the 
advantage  of  erecting  low-roofed  conservatories,  especially  when 

*  See  Ventilation. 


STRUCTURES  ADAPTED  TO  PARTICULAR  PURPOSES.      83 

the  object  is  to  grow  the  plants  in  beds,  or  masses,  irregularly 
placed  on  the  level  of  the  floor,  which  is  decidedly  an  improve- 
ment upon  the  old  method,  of  having  a  few  long-legged  and 
branchless  specimens  sticking  their  heads  up  to  the  glass,  where 
their  leaves  and  flowers  are  far  above  the  common  axis  of  vision, 
and  where  nothing  is  seen  below  but  the  monotonous  bed,  and 
the  bare  stems  of  the  plants  that  are  growing  in  it,  compelling 
the  gardener,  at  all  hazard  of  propriety,  and  in  violation  of 
every  principle  of  taste,  as  well  as  of  his  own  judgment,  to  stick 
in  the  commonest  plants,  whatever  they  are,  among  the  bare 
stems  of  the  others,  to  fill  up  the  unsightly  blanks  and  vacancies 
thus  occasioned  in  the  beds. 

While  on  this  subject,  we  will  just  briefly  remark,  that  nothing 
has  so  much  tended  to  improve  the  culture  of  the  trees  and 
shrubs,  generally  grown  in  houses  of  glass,  as  the  improvement 
that  has  taken  place  in  the  mode  of  construction.  All  practical 
men  are  agreed  on  the  point,  that,  to  grow  plants  well,  the 
house  must  be  low  in  the  roof,  and  light  as  well  as  air  must  be 
admitted  freely  to  every  part  of  the  plant,  from  the  ground  to 
the  glass.  They  must  also  be  situated  in  such  a  way,  regarding 
their  lower  parts,  that  the  light  may  not  be  obstructed,  for  how- 
ever powerful,  and  perhaps  sometimes  injurious,  the  fierce 
rays  of  the  mid-day  sun  may  be  in  mid-summer,  yet  its  perma- 
nent obstruction  is  far  more  so.  It  is  easier  to  obviate  scorching 
in  the  one  case,  than  etiolation  in  the  other. 

8 


SECTION    IV. 

INTERIOR     ARRANGEMENTS. 

1.  ARRANGEMENTS  for  the  interior  of  forcing-houses,  culinary- 
houses,  &c.,  are  generally  very  much  alike,  consisting  chiefly 
of  trellises  of  wood,  or  of  wire,  to  which  the  trees  are  trained. 
The  other  portions  of  interior  detail  are  common  to  horticultural 
structures  of  every  description,  and  will  be  subsequently  de- 
scribed in  their  respective  places. 

"Half  the  advantages,"  says  Loudon,  (Ency.  of  Gard.,)  "of 
culture,  in  forcing-houses,  would  be  lost  without  the  use  of  trel- 
lises. On  these  the  branches  are  readily  spread  out  to  the  sun, 
of  whose  influence  every  branch,  and  every  twig,  and  every  leaf, 
partake  alike ;  whereas,  were  they  left  to  grow  as  standards,  un- 
less the  house  were  glass  on  all  sides,  only  the  extremities  of 
the  shoots  would  enjoy  sufficient  light.  The  advantages,  in 
respect  of  air,  water,  pruning,  and  other  parts  of  culture,  are 
equally  in  favor  of  trellises,  independently,  altogether,  of  the 
influence  which  proper  training  has  upon  fruit-trees,  as  the  vine, 
the  peach,  apricot,  &c.,  to  produce  fruitfulness." 

Notwithstanding  the  obvious  utility  of  trellises  in  culinary 
houses,  the  use  of  them  is  frequently  carried  to  a  most  unprofit- 
able and  injurious  extent,  when  the  whole  interior  of  the  house 
is  filled  with  foliage  from  the  glass  to  the  floor.  Here,  work  is 
entailed  upon  the  gardener  to  no  purpose ;  and  though  good 
crops  may  be  borne  on  the  trees  that  are  trained  upon  the  trel- 
lises crossing  the  house,  or  on  the  back  wall,  the  fruit  is  utterly 
worthless. 

The  trellis,  situated  on  the  back  wall,  was  formerly  considered 
the  principal  part  of  the  house,  for  producing  a  crop ;  but  this 
is  only  the  case  in*  small,  narrow  houses,  and  where  no  trees 
are  trained  upon  the  rafters,  or  under  the  glass.  Experience 
has  proved  that,  where  the  whole  surface  of  the  glass  is  covered 


INTERIOR    ARRANGEMENTS.  85 

with  foliage,  there  is  very  little  gained  by  training  either  peaches 
or  vines  on  the  back  wall. 

The  principal  use  to  which  back-wall  trellises  may  be  profita- 
bly turned,  is  for  the  cultivation  of  figs,  which  are  found  to  do 
much  better  than  peaches  under  the  shade  of  others. 

The  trellis,  whatever  its  form,  should  be  as  near  to  the  glass 
as  possible,  and  placed  so  as  to  command  the  full  influence  of 
the  light  entering  the  house.  When  the  vines  are  trained  upon 
the  single  rafter  trellis,  Fig.  28,  A,  leaving  the  middle  of  the 
lights  open,  for  the  free  admission  of  light  to  plants  beneath,  then 
the  curvilinear  trellis  may  be  introduced  into  the  centre  of  the 
house,  as  represented  at  a,  Fig.  29,  from  which  good  peaches 
and  nectarines  may  be  obtained,  providing  the  sashes  be  kept 
open  in  the  middle,  as  already  stated,  for  the  admission  of  the 
unobstructed  light. 

Fig.  28. 
A.  B.  C. 


The  most  common  method  of  fixing  the  roof  trellis  is  by  studs, 
Fig.  28,  B,  screwed  into  the  rafter,  about  eight  inches  distant. 
Each  stud  is  provided  with  an  eye,  or  hole,  at  the  extremity, 
through  which  the  wire  is  passed,  and  tightened  at  both  ends 
by  screws  and  nuts.  The  studs  should  not  be  less  than  twelve 
inches  in  length,  so  as  to  afford  room  for  the  foliage  to  expand 
itself  fully,  without  coming  in  contact  with  the  glass,  which, 
when  moistened  with  the  condensed  vapor,  is  apt  to  scald  the 
leaves  that  happen  to  be  touching  it.  The  wires  forming  the 
trellis  are  stretched  horizontally  from  both  ends  of  the  roof,  at 
about  nine  inches  distant. 

Instead  of  studs  screwed  into  the  rafter,  the  horizontal  wires 
may  be  fixed,  and  kept  in  their  places,  by  rods  of  iron,  having 
holes  for  the  wires  passing  through,  at  regular  distances.  These 


86 


INTERIOR    ARRANGEMENTS. 


rods  are  attached  by  a  loop  and  staple  to  the  front  wall  at  the 
lower  end,  and  to  the  back  wall  at  the  upper.  This  method  is 
preferable  to  having  the  studs  screwed  into  the  rafter,  as  they 
can  be  easily  removed,  or  the  whole  tegument  of  trellis  may, 
if  desired,  be  taken  down  and  put  up  again  without  much 
trouble.  This  is  of  great  importance  on  occasions  of  cleaning 
and  painting  the  sashes,  etc.  Fig.  28,  C,  shows  the  perforated  rod 
which  is  here  referred  to,  the  looped  end  being  fixed  in  common 
staples. 

When  provision  is  made  for  a  middle  trellis,  this  should 
always  have  a  curvilinear  shape,  as  in  a,  Fig.  29.     This  form 

Fig.  29. 


affords  not  only  the  largest  training  surface,  but  presents  a 
larger  surface  to  the  light,  than  any  other  form  that  can  be 
adopted,  and,  what  is  of  more  importance  in  regard  to  small 
houses,  it  occupies  less  room  in  proportion  to  its  training  surface 
than  any  other  trellis  with  which  we  are  acquainted. 

Cross-trellises,  or  horizontal  upright  trellises  in  the  middle  of 
the  house,  not  only  destroy  the  effect  within,  but  are  worse  than 
useless.  Where  the  house  is  of  sufficient  size  to  admit  of  a 
middle  trellis,  and  a  sufficiency  of  roof-surface  to  afford  the  cen- 
tre of  the  sashes  to  be  kept  clear  of  foliage,  we  should  prefer 
having  a  sloping  trellis  on  the  back  wall,  and  the  centre  bed 
occupied  with  dwarf  standards,  planted  either  in  a  straight  or 
zig-zag  line  along  the  border,  which,  under  good  management, 
will  be  as  fruitful  as  if  trained  on  a  trellis,  while  their  appear- 
ance would  be  pleasing  and  handsome.  Fig.  29  will  convey  a 
better  idea  of  our  method  than  by  description.  Fig.  30  shows 
the  same  system  carried  out  in  a  double-roofed  house. 

Trellises  are  now  made  generally  of  wire,  as  being  cheaper 


INTERIOR   ARRANGEMENTS. 

Fig.  30. 


87 


Fig.  31. 


and  lighter  than  wood.  Wire  is  in  every  way  fitter  for  the 
purpose  than  wood,  especially  for  roof  trellising.  The  distance 
at  which  the  wires  should  be  placed  apart  depends  upon  the 
kind  of  trees  to  be  trained  to  them.  For  grapes,  the  distance 
should  be  12  or  14  inches ;  and  for  peaches,  nectarines,  and 
small-wooded  trees,  not  more  than  8  inches.  The  distance  of 
the  wires  of  the  roof  trellis  from  the  glass  should  not  be  less 
than  one  foot  for  grapes,  and  for  peaches  and  other  similar  trees 
not  less  than  ten  inches.  In  properly  constructed  houses,  there 
should  always  be  a  lower  trellis,  with  the  wires  placed  at  double 
the  distance  of  the  others,  for  training  the  summer  shoots  to,  to 
prevent  the  crowding  of  the  vine  branches  when  the  trees  are 
full  of  fruit,  in  order  that  there  may  not  be  a  confusion  of  fruit 
and  foliage.  Vines,  or,  indeed,  any  other  kind  of  fruit  trees, 
should  never  be  nailed  to  the  wood  of  the  house ;  but,  in  all 
cases,  trained  at  some  distance  from  it,  however  little  room  there 
may  be  for  that  purpose. 

2.     The  interior  of  the  green-house  is  generally  provided  with 
a  stage  in  the  centre,  and  shelves  round  the  sides,  on  which  the 
8* 


88 


INTERIOR    ARRANGEMENTS. 


plants  are  arranged;  and  this  is  the  principal  object  which 
demands  our  attention.  In  single-roofed  houses,  the  stage  gen- 
erally rises  towards  the  back  wall ;  but  in  span-roofed  houses, 
which  are  surrounded  by  a  path,  the  stage  or  platform  rises 
from  both  sides,  and  meets  in  the  middle  of  the  house. 

It  is  a  principle  with  some  people  to  place  the  stage  on  the 
same  angle  as  the  roof,  i.  e.,  each  shelf  rising  at  an  equal  dis- 
tance from  the  plane  of  the  rafters.  This,  however,  is  a  bad 
rule,  and,  in  cases  where  the  roof  is  very  steep,  will  make  a 
wretched  receptacle  for  green-house  plants,  No  general  rules 
can  be  laid  down  for  the  erection  of  the  stage,  as  this  will  very 
much  depend  upon  the  form  and  size  of  the  house.  We  might 
add,  however,  that  the  angle  of  the  stage  ought  never  to  exceed 
the  angle  of  the  roof,  but,  if  practicable,  should  be  rather  flatter 
than  otherwise,  to  admit  of  larger  plants  being  placed  on  the 
upper  shelves,  which  serve  to  give  the  house  a  larger  and  more 
effective  appearance  from  the  inside  view. 

Green-houses  intended  for  the  growth  of  a  promiscuous  col- 
lection of  plants,  some  of  which  may  reach  a  considerable 
height,  should  have  but  few  shelves  on  the  platform,  say  three 
or  four  rises  are  quite  sufficient,  leaving  the  upper  shelves,  at 
least,  twice  the  width  of  the  others.  This  applies,  also,  to  sin- 
gle-roofed houses.  Many  commit  an  error  in  making  their 
stages  not  only  too  steep,  but  the  shelves  too  narrow  and  too 
high,  individually.  The  shelves  of  a  green-house  for  displaying 
plants  ought  not  to  be  less  than  one  foot  in  width,  this  width 
increasing  towards  the  top  shelf,  and  not  more  than  eight  or 
•nine  inches  in  height  from  each  other. 

Houses  appropriated  to  the  growth  of  small  plants,  as  nurse- 
rymen's stock-houses,  propagating,  etc.,  may  be  staged  much 
closer  than  this.  These  remarks  chiefly  apply  to  the  green- 
houses of  private  individuals,  and  houses  for  the  exhibition  and 
arrangement  of  a  general  collection  of  plants. 

3.  Conservatories,  orangeries,  and  houses  for  the  growth 
of  the  palm  family,  have  pits,  or  more  properly  beds,  in  which 
plants  are  planted  out.  These  beds  are  sometimes  level  with 
the  floor,  and  sometimes  raised  above  it,  being  enclosed  by  a 


INTERIOR   ARRANGEMENTS.  89 

curb.  The  principles  of  culture  in  these  houses  being  some- 
what different  from  the  common  green-house,  it  is  necessary 
that  they  be  arranged  to  suit  the  plants  grown  in  them. 

The  general  form  of  conservatory  beds  is  exactly  that  of  the 
structure.  If  the  house  be  a  parallelogram,  the  bed  has  the 
same  form,  sometimes  divided  in  the  middle  by  a  path,  and 
sometimes  surrounded  by  a  path  on  both  sides.  These  structures, 
when  properly  built  and  managed,  are  undoubtedly  the  means 
of  conferring  on  lovers  of  gardening  and  flowers,  enjoyment  of 
the  highest  and  purest  character.  When  a  fine  conservatory  of 
this  kind  is  attached  to  the  mansion  house,  or  connected  with  it 
by  a  glazed  arcade,  it  forms  one  of  the  most  delightful  prome- 
nades in  winter  that  wealth  and  taste  can  command. 

There  is  undoubtedly  much  yet  to  be  done  in  the  way  of 
improving  the  interior  of  ornamental  conservatories,  not  only  as 
regards  their  adaptability  to  plant  culture,  but  also  their  general 
effect.  We  seldom  see  anything  else  than  the  same  flat,  formal 
bed  or  border,  which  is  either  rectangular,  round,  or  square, 
according  as  the  form  of  the  building  may  determine  by  its 
walls.  Even  the  refinement  or  elegancies  of  construction  of 
architecture  fail  to  invest  such  buildings  with  any  character 
of  distinctness  or  novelty,  owing  to  the  sameness  or  monotony 
which  forms  the  basis  of  the  design.  As  far  as  relates  to  the 
exterior,  a  considerable  improvement  is  taking  place  from  the 
use  of  curvilinear  roofs,  and  lighter  and  more  elegant  workman- 
ship, and  also  resulting  from  the  adoption  of  double-roofed 
houses,  instead  of  the  dark,  dull,  narrow,  clumsy  shed-like  erec- 
tions which  formerly  used  to  be  erected,  and  the  various  forms 
of  elevation,  which  are  now  so  generally  arranged  as  to  produce 
a  very  pleasing  and  picturesque  effect. 

A  recent  and  very  general  improvement  in  the  construction 
of  green-houses,  consists  in  making  the  stages  and  shelves  of 
slate,  or  thin  plates  of  stone ;  this  practice  is  now  common  about 
London.  These  slates  are  frequently  grooved  or  hollowed  out 
so  that  the  water  is  retained  under  the  pots,  and  thus  dripping 
is  prevented,  and  evaporation  is  provided  for  in  dry  weather. 
This  may  be  considered  as  a  real  improvement,  which  is  proved 
by  the  readiness  with  which  this  practice  was  adopted  by  prac- 


90  INTERIOR   ARRANGEMENTS. 

tical  gardeners  and  nurserymen,  and,  from  the  cool  nature  of 
that  material,  deserves  to  be  more  extensively  followed  in  orna- 
mental green-houses  in  this  country. 

The  irregular  method  of  laying  out  the  interior  of  conservato- 
ries, which  promises  to  subvert  the  formal  and  monotonous 
arrangements  of  the  old  school,  is  one  of  the  greatest  steps 
towards  a  higher  and  more  natural  taste  of  artificial  gardening 
than  any  other  that  has  taken  place  in  this  department  of  the 
art  for  the  last  fifty  years,  inasmuch  as  it  can  be  carried  out 
with  equal  advantage  on  a  large,  as  well  as  on  a  small,  scale ; 
and  where  this  method  is  applied  to  a  large  structure,  i.  e., 
a  structure  covering  a  large  area  of  ground,  it  necessarily  leads 
to  the  adoption  of  interior  arrangements,  as  far  surpassing  the 
old  method  in  beauty  and  effect  as  it  does  in  respect  to  econ- 
omy, convenience,  and  comfort. 

When  we  visit  a  conservatory  lately  erected,  and  see  it  to  be 
a  perfect  fac  simile  of  others  that  had  been  erected  a  century 
before,  there  is  positively  nothing  to  strike  us  with  admiration, 
except,  perhaps,  the  character  of  its  architecture.  When  we 
see,  in  the  costly  erection  before  us,  the  exact  image  of  conser- 
vatories everywhere  else,  the  object  loses  one  half  of  the  charms 
of  novelty  and  interest.  It  is,  in  fact,  in  the  endless  variety  and 
intrinsic  beauty  of  which  they  easily  admit,  that  their  chief 
fascination  rests.  This  is  the  case  with  all  other  objects  of  art ; 
with  private  mansions,  for  instance.  How  monotonous  and  tire- 
some would  a  country  or  suburb  be,  were  every  mansion  and 
dwelling  an  exact  copy  of  the  other !  And  why  should  it  be  so 
with  erections  for  the  growth  of  plants  ?  Why  should  these, 
which  are,  to  a  certain  extent,  invested  with  the  charm  of  rarity, 
be  deprived  of  the  charm  of  variety  ?  Why  should  there  not 
be  groves,  and  lakes,  and  irregular  flower  beds,  and  rocks,  and 
aquariums,  and  caverns,  and  jets,  and  waterfalls  within  as  well 
as  without?  In  the  former  case,  their  beauties  would  be  avail- 
able, either  for  recreation,  admiration,  or  study,  at  all  seasons ; 
in  the  latter,  the  fickleness  and  vicissitudes  of  our  climate  fre- 
quently prevent  the  enjoyment  of  either. 

The  finest  illustration  of  this  system  with  which  we  are 
acquainted,  is  in  the  beautiful  conservatory  of  the  Royal 


INTERIOR    ARRANGEMENTS.  91 

Botanic  Society's  Garden,  in  the  Regent's  Park,  by  Mr.  Mar- 
nock,  and  which  is,  perhaps,  one  of  the  best  adapted  structures 
for  the  growth  of  plants  in  England,  and  is  decidedly  superior 
to  the  many  monster  plant-houses  lately  erected  in  that  country. 
We  have  compared  this  structure  with  the  large  houses  at 
Chatsworth,  Kew,  Sion  House,  and  other  places,  and,  whether 
in  respect  to  convenience  arid  comfort,  general  appearance  or 
adaptability,  we  consider  it  in  every  way  preferable  to  any  other 
structure  of  the  kind  we  have  seen.  This  splendid  winter- 
garden —  for  its  great  size  justly  entitles  it  to  this  name  — 
contains  collections  of  different  degrees  of  hardiness,  and  em- 
braces climates  suitable  to  each.  Its  walks  are  gravelled,  like  a 
flower-garden,  winding  through  amongst  the  various  groups  of 
plants;  sometimes  overhung  with  the  pendulous  branches  of 
flowering  plants  of  great  size  and  beauty,  and  sometimes  wind- 
ing beneath  arches  and  arbors  of  climbers  in  wild  profusion. 
Here  you  climb  over  rocks,  covered  with  characteristic  plants, 
and  there  you  descend  into  the  humid  recesses  of  orchids  and 
aquatics.  This  house  has  not  the  domed  and  lofty  character  of 
some  other  structures  of  the  kind,  which  is  at  once  a  prominent 
feature  and  a  prominent  fault  in  their  construction ;  it  consists 
of  several  spans,  supported  on  light  iron  columns,  the  centre  one 
being  somewhat  higher  than  the  others ;  and,  though  having 
little  pretensions  to  what  is  generally  called  architectural  dis- 
play, yet  its  commanding  position  and  its  magnitude  strike  the 
observer  with  a  feeling  of  admiration,  which  is  only  surpassed 
by  its  internal  arrangements. 

The  general  system  of  building  conservatories  in  a  recess 
of  the  mansion  is  entirely  subversive  of  this  method  of  internal 
arrangement,  because  of  their  total  inadaptability  for  this  pur- 
pose. It  must  not  be  supposed,  however,  that  there  is  any  abso- 
lute reason  for  detaching  the  conservatory  from  the  mansion,  if 
it  be  otherwise  desired ;  but  it  ought  to  be  there  as  a  positive 
part  of  the  building,  not  a  tributary  attachment  to  fill  up  a  cor- 
ner. That  these  kinds  of  structures  for  plants  are  being  rapidly 
improved,  is  evident,  and  this,  indeed,  must  be  the  case,  since 
the  improvement  here  spoken  of  springs  from  necessity.  The 
attachment  of  a  green-house  to  a  mansion  appears  to  us  in  as 


92  INTERIOR   ARRANGEMENTS. 

questionable  taste,  as  placing  the  conservatory  in  the  middle  of 
the  kitchen  garden,  or  in  the  orchard ;  and  if  any  kind  of  hor- 
ticultural structure  is  to  be  attached  to  the  mansion,  it  ought, 
by  all  means,  to  be  a  conservatory. 

As  an  illustration  that  conservatories  may  form  prominent 
portions  of  a  mansion,  or  even  a  whole  wing  of  it,  without 
destroying  its  architectural  character,  we  might  point  to  a  design, 
in  the  December  number  of  the  "Horticulturist"  for  1849,  by  A.  J. 
Downing,  Esq.,  of  Newburgh,  which  is  introduced  to  show  how 
a  simple  structure  of  this  kind  ought  to  be  treated  so  as  to  give 
the  whole  an  architectural  and  harmonious  character,  and  show- 
ing, also,  how  this  may  be  accomplished  without  rendering  the 
conservatory  opaque  on  either  side,  except  the  one  end  by  which 
it  is  attached  to  the  house,  —  a  circumstance  which  will  be 
indispensable  in  conservatories  attached  to  houses,  unless  they 
be  joined  by  means  of  a  veranda,  which  gives  them  somewhat 
of  an  isolated  character.  This  house  which  we  have  referred 
to  is  the  kind  of  conservatory  which  we  like,  being  satisfied, 
from  experience,  that,  unless  they  be  constructed  somewhat 
after  this  method,  they  can  never  give  the  proprietors  that  satis- 
faction which  they  have  a  right  to  expect ;  and  we  trust  Mr. 
Downing  will  go  on  with  creations  of  this  kind,  till  these  trans- 
parent conservatories  become  more  general  than  they  are  at 
present. 

Although  it  is  not  necessary,  on  account  of  perfect  adapta- 
bility, to  place  conservatories  apart  from  dwelling-houses,  yet 
we  generally  find  that  structures,  standing  detached  from  the 
mansion,  are  better  suited  for  the  growth  of  plants  :  first,  because 
there  is  less  temptation  to  introduce  massive  workmanship,  on 
purpose  to  harmonize  with  the  house ;  and,  secondly,  there  is, 
in  most  instances,  more  facility  of  making  the  house  to  satisfy 
the  requirements  of  vegetation,  and,  consequently,  less  likelihood 
of  departing  from  the  principles  of  erection  which  science  and 
practice  have  determined  as  essential  to  the  successful  cultiva- 
tion of  plants. 

In  many  instances,  it  is  absolutely  impossible  to  comply  with 
these  principles,  whatever  interior  arrangements  may  be  adopted. 
Where  the  conservatory  is  a  mere  lean-to,  stuck-in  attachment, 


INTERIOR    ARRANGEMENTS. 


compliance  with  the  principle  of  plant-culture,  or  with  the 
method  of  interior  arrangement  which  we  have  here  recom- 
mended, is  equally  impossible.  In  the  latter  case,  the  greater 
portion  of  the  plant-house  must  necessarily  be  formed  by  the 
walls  of  the  building,  and  the  shadow  of  its  elevated  parts  will 
be  thrown  upon  the  plant-house  for  at  least  one  half  the  day. 
This  is  nearly  as  injurious  as  if  the  portions  thus  shaded 
were  opaque.  The  only  way  of  obviating  the  evils  consequent 
upon  its  position,  is  to  give  every  possible  inch  of  light  to  the 
one,  to  enable  it  to  counterbalance  the  shade  which  it  must  bear 
from  the  other. 

When  plants  are  planted  in  beds  in  the  conservatory,  they 
require  to  be  large  specimens,  otherwise  they  have  a  meagre 
appearance,  and  must  be  a  great  distance  from  the  roof,  and 
this  is  one  of  the  greatest  difficulties  the  gardener  has  to  contend 
with.  It  must  be  borne  in  mind  that  fine  specimens  do  not 
consist  in  plants  that  reach  from  the  bed  to  the  glass,  with  naked 
stems,  and  only  a  few  branches  at  the  top,  which  is  invariably 
the  result  of  lofty  roofs  and  dark  walls. 

We  have  already  shown,  in  the  preceding  section,  the  conse- 
quence of  high-roofed  houses,  and  the  difficulty  of  managing 
them  in  a  manner  fitted  for  the  successful  cultivation  of  plants ; 
and  if  high-domed  or  right-lined  roofs  be  improper  in  houses 
where  the  plants  are  elevated  on  shelves  and  stages,  they  are 
much  more  so  where  the  plants  are  set  in  the  beds  without  pots, 
as  the  distance  from  the  light  renders  it  impossible  for  them  to 
grow  bushy  and  branching  below.  These,  when  included  within 
the  common-place  curb  of  a  square,  or  a  parallelogram,  or  an 
oval,  or  circle,  which  are  little  better,  (except  when  sparingly 
introduced,  and  only  where  they  are  described  by  the  natural 
curves  of  the  contiguous  figures,)  invariably  produce  an  effect 
so  common-place  and  uninteresting,  as  to  fail  in  exciting  the 
faintest  emotions  of  pleasure,  or  novelty,  or  interest,  in  one  out 
of  a  hundred  individuals  of  taste  and  judgment. 


94  INTERIOR   ARRANGEMENTS. 


REFERENCE   TO  FIG.  32. 

A,  A,  A,  A,  A,  A,  Beds  in  which  the  plants  are  set  out  and 

arranged  according  to  their  methods  of  growth,  habits, 
height,  &c. 

B,  Water  Tank,  with  jet  in  the  centre.     This  tank  is  surround- 

ed by  rock-work  and  characteristic  plants. 

C,  C,  Seats  on  each  side  of  the  jet,  commanding,  also,  views  of 

the  surrounding  grounds. 

D,  D,  i),  D,  Conduit  for  the  hot-water  pipes,  for  warming  the 

structure.  This  open  conduit  passes  along  the  wall  the 
whole  length  and  breadth  of  the  house,  and  is  covered  with 
grating,  which  serves  as  a  path  for  watering,  and  conduct- 
ing the  necessary  operations  connected  with  the  culture  of 
the  plants. 

jE,  £,  E,  an  open  Balcony,  passing  all  round  the  house,  and 
surrounded  by  a  balustrade.  This  balcony  forms  a  contin- 
uation of  the  pqrch  on  the  one  side,  and  runs  out  upon  the 
ground-level  on  the  other.  From  this  balcony  are  seen 
the  garden,  the  lakes,  the  hot-house,  and  the  ornamental 
grounds.  The  chief  purpose  of  this  balcony,  however,  is 
to  maintain  the  ground-level  of  the  floor,  and  to  make  the 
conservatory  in  harmony  with  the  mansion,  without  de- 
stroying its  adaptability  as  a  first-rate  plant-house,  of  that 
class  intended  for  growing  large  specimens,  planted  out  in 
the  ground. 

F,  Steps,  leading  from  the  balcony  into  the  pleasure-grounds. 

G,  Door  opening  from  the  drawing-room. 

H,  Rock-work  for  alpine  plants,  surrounding  the  aquarium  and 

jet. 
For  end  view  of  this  house,  see  Frontispiece. 


INTERIOR   ARRANGEMENTS. 


Fig.  32. 


96  INTERIOR    ARRANGEMENTS. 

Conservatories  are,  probably,  the  most  important  structures 
used  in  ornamental  gardening;  and,  as  we  have  already  said  in 
regard  to  other  kinds  of  horticultural  buildings,  we  say,  also,  of 
them,  that  no  degree  of  gardening  ability,  and  practical  attention 
on  the  part  of  the  gardener,  will  compensate  for  the  want  of  light 
and  air;  and,  where  the  arrangements  for  the  working  of  the 
house,  in  regard  to  air,  heat,  &c.,  are  imperfect,  the  risk  is  great, 
and  it  is  painful  for  a  skilful  and  zealous  gardener  to  contem- 
plate the  consequences  which  he  may  be  unable  to  prevent. 
One  single  night  may  destroy  the  labors  of  years  past,  and  for- 
bid hope  for  years  to  come ;  and,  after  all,  the  blame  may  be 
laid  where  it  is  least  merited,  and  censure  withheld  from  the 
party  who  most  deserved  it. 

In  all  buildings,  and  especially  conservatories,  the  most  com- 
plete and  elegant  design,  when  badly  executed,  is  disagreeable 
to  the  view,  defective  in  the  object  of  its  erection,  and  ruinous  to 
the  proprietor,  because  it  is  incapable  of  giving  that  satisfaction 
and  pleasure  which  he  was  entitled  to  expect  from  his  outlay. 

Fig.  32  is  the  ground  plan  of  a  conservatory,  which  we  have 
designed  for  erection  at  a  gentleman's  country-seat.  It  is  in- 
tended to  form  a  prominent  wing  of  the  mansion.  The  structure 
is  entered  at  one  end  by  a  door,  leading  from  the  principal 
apartments  of  the  house.  The  conservatory  is  traversed  by 
curved  walks,  laid  with  marble,  and  bordered  by  a  curb,  on  each 
side,  of  the  same  material.  In  the  centre  is  a  basin  of  water, 
with  a  jet  playing  over  a  rockery,  as  seen  in  the  cut,  Fig.  32. 
In  this  design  we  have  endeavored  to  combine  perfect  adapta- 
bility, with  beauty  in  the  structure,  and  harmony  in  the  whole. 

This  method  of  laying  out  the  interior  of  a  conservatory 
admits  of  the  most  perfect  arrangement  in  the  planting  of  the 
beds  and  compartments,  intended  for  the  exotic  trees  and  shrubs, 
with  which  the  structure  is  to  be  filled.  The  walks  wind 
through,  among  the  plants,  as  in  a  common  shrubbery,  or  flower- 
garden  ;  and,  when  the  compartments  are  tastefully  arranged, 
and  the  whole  kept  in  healthiness  and  luxuriance,  with  climbing 
plants  hanging  in  festoons  from  the  rafters  and  other  supporters 
of  the  roof,  it  forms  decidedly  the  most  delightful  and  satisfac- 
tory kind  of  horticultural  structure  that  can  be  erected  for  com- 
fort, convenience,  and  enjoyment. 


INTERIOR   ARRANGEMENTS.  97 

We  do  not  think  that  any  definite  rule  can  be  laid  down  for 
the  laying  out  of  the  area  of  a  conservatory,  as  the  formation  of 
the  beds  and  walks  may  be  dictated  by  the  taste  of  the  proprietor, 
or  those  in  whom  he  confides  the  management  of  the  work. 
Almost  any  curve  may  be  adopted  in  the  walks,  without  destroy- 
ing the  effect  of  the  interior  view.  What  we  condemn  is  the 
monotonous  straight  lines  by  which  the  area  is  generally  laid 
out.  It  must  be  observed,  however,  that  this  method  is  entirely 
inapplicable,  unless  the  house  be  glazed  on  at  least  three  sides, 
and  the  roof  so  constructed  as  to  admit  the  greatest  possible 
quantity  of  light  in  proportion  to  the  extent  of  the  area  enclosed. 
The  roof  should,  also,  be  as  low  as  is  consistent  with  exterior 
effect,  and  the  admission  of  plants  of  good  size ;  for,  as  we  have 
already  observed,  one  of  the  prevailing  errors  in  the  construction 
of  conservatories  adjoining  mansions  consists  in  their  being 
made  too  lofty  and  too  opaque.  They  are  designed  generally  to 
suit  the  place  of  the  building,  without  regard  to  the  effect  of  the 
conservatory  itself,  as  a  structure,  or  as  a  plant-house. 

There  are  many  other  advantages,  resulting  from  houses  of 
this  description,  which,  in  a  practical  point  of  view,  are  deserv- 
ing of  consideration.  Not  the  least  of  these  is  the  facility  with 
which  plants  can  be  arranged  to  produce  the  best  possible  effect. 
Plants  are  much  easier  arranged  within  curved  lines,  than  in 
squares  or  parallelograms ;  and  the  curvatures  of  the  beds  are 
always  more  spirited  and  pleasing  than  continuous  straight 
lines,  whatever  the  house  may  be  filled  with,  or  however  badly 
the  plants  may  be  disposed. 

We  have  only  room  to  notice  one  feature  more  in  the  con- 
struction of  this  conservatory,  viz.,  the  form  of  the  roof.  We 
have  chosen  the  spans  of  different  sizes,  in  preference  to  one 
single  span,  as  much  for  adaptability  as  to  harmonize  with  the 
architecture  of  the  mansion.  This  system  tends  to  prevent  the 
accumulation  of  warm  air  at  the  top  of  the  house,  and  hence 
the  heat  is  distributed  more  equally  among  the  plants.  For  the 
same  reason,  ventilators  are  provided  at  the  top  of  each  span,  so 
that  the  external  air  admitted,  as  well  as  the  artificial  heat  ris- 
ing upwards,  will  be  more  equally  distributed  over  the  house.1* 

*  For  further  notice  of  this,  see  Ventilation. 


98  INTERIOR   ARRANGEMENTS. 

An  end  view  of  this  structure  is  shown  in  the  frontispiece.  As 
the  ground,  in  this  case,  descends  gradually  from  the  base  of  the 
mansion,  a  considerable  depth  of  parapet  wall  is  necessary  to 
bring  the  floor  of  the  conservatory  to  the  desired  level,  and  the 
requisite  distance  from  the  roof.  Curved  roofs  can  only  be 
adopted  where  the  building  admits  them  without  jarring  dis- 
cordantly with  the  general  architecture,  and,  in  some  instances, 
straight-lined  roofs  will  be  preferable ;  but  in  all  cases  where 
curvilinear  roofs  can  be  made  to  harmonize  with  the  building, 
they  are  decidedly  to  be  preferred,  on  account  of  the  superior 
beauty  of  curved  lines  viewed  in  contrast  with  the  surrounding 
scenery,  and  also  on  account  of  the  superior  beauty  of  the  struc- 
ture from  within,  in  harmony  with  curved  figures  of  the  walks 
and  borders  of  a  house,  such  as  that  we  have  here  described. 


SECTION    V. 

MATERIALS     OF     CONSTRUCTION. 

1.  Workmanship.  —  However  excellent  and  adaptable  may 
be  the  design  of  a  horticultural  erection,  if  the  work  be  badly 
executed  the  structure  will  generally  be  defective  in  the  work- 
ing, and  the  trouble  of  management  will  be  greatly  increased. 
Bad  foundations,  bad  roofs,  bad-fitting  sashes,  rendering  them 
difficult  to  open  and  shut,  bad  glazing,  and  bad  workmanship  of 
every  description,  are  too  common  to  exist  without  being  a  very 
perceptible  evil,  and  one  that  is  much  complained  of  by  practical 
gardeners,  upon  whom  the  consequences  of  this  method  of  con- 
struction generally  fall.  In  all  regular  work,  coming  under  the 
province  of  the  architect  or  engineer,  there  is  generally  particu- 
lar attention  directed  to  the  facility  of  working,  and  ingenuity 
is  exerted  to  its  utmost  limits  to  perfect  and  simplify  those 
facilities,  however  temporarily  the  structure  or  work  may  be 
constructed.  But  horticultural  buildings,  relatively  to  civil 
architecture,  appear  to  be  an  anomalous  class  of  structures,  not 
coming  strictly  within  the  province  of  the  architect,  —  except 
in  so  far  as  they  may  be  related  to  the  house  in  an  architectural 
point  of  view,  —  and  hence  they  are  more  the  subject  of  chance 
or  caprice  in  design,  and  of  local  convenience  in  execution, 
than  any  other  department  of  rural  architecture.  The  subject 
of  horticultural  architecture  has  not  been  deemed  of  sufficient 
importance  to  induce  civil  architects  to  make  themselves  ac- 
quainted with  the  principles  on  which  plant-houses  should  be 
constructed,  or  to  consider  the  nature  of  workmanship  in  relation 
to  its  work ;  and,  consequently,  the  construction  of  horticultural 
buildings  is  either  left  wholly  to  gardeners,  who  understand 
little  of  the  science  of  architecture,  or  wholly  to  architects,  who 
understand  as  little  of  the  science  of  horticulture.  The  conse- 
quence, in  either  case,  is  generally  incongruity  in  appearance, 
9* 


100  MATERIALS    OF   CONSTRUCTION. 

want  of  success  in  the  useful  results,  and  want  of  permanency 
in  the  structure  itself.  In  every  country,  no  doubt,  such  cases 
are  numerous,  but  here,  they  are  more  numerous  probably  than 
in  any  other,  arising,  no  doubt,  from  that  want  of  attention  to 
the  details  of  horticultural  architecture,  and  to  the  still  unde- 
veloped principles  of  science,  upon  which  it  is  based. 

The  temporary  and  inferior  character  of  the  workmanship 
generally  bestowed  on  horticultural  erections  is  a  source  of  great 
loss  to  those  erecting  such  buildings,  and  demands  the  serious 
attention  of  all  who  contemplate  the  construction  of  them.  The 
remarks,  which  have  been  applied  by  a  popular  writer  on  farm- 
ing in  regard  to  farm-buildings,  are  still  more  applicable  to  build- 
ings for  the  purposes  of  horticulture.^  Buildings,  manifestly 
intended  to  be  permanent,  are  put  up  to  stand  for  a  year  or  two, 
when  it  becomes  absolutely  necessary  to  their  continuation,  to 
spend  a  sum  upon  them  equal  to  one  third  the  cost  of  their 
original  erection,  which  acts  as  a  drawback  upon  the  progress 
of  horticulture  in  this  country,  as  many  suppose  that  this  early 
additional  expenditure  is  merely  the  consequence  which  the  com- 
mon tear  and  wear  of  time  entails  upon  all  such  structures ;  and 
hence  they  are  considered  too  expensive  to  keep  in  order,  even 
though  willing  to  go  to  the  cost  of  original  construction.  Now 
experience  has  taught  us  that  structures,  substantially  con- 
structed at  the  first,  and  of  good  materials,  will  stand  for  at  least 
twenty  years  without  any  additional  outlay,  save  a  few  coats  of 
paint  during  that  period,  which  increases  their  durability,  the 
oftener  it  is  applied. 

We  have  been  induced  to  dwell  longer  on  the  subject  of 
workmanship,  from  the  numerous  examples  which  have  come 
under  our  own  observation,  and  from  the  trouble  and  annoyance 
to  which  we  are  almost  daily  subjected  on  this  account.  In 
small  erections,  the  inconveniences  arising  from  bad  workman- 

*  Few  things  serve  better  to  distinguish  the  habits,  and  even  the 
characters,  of  the  progeny  from  the  parent  stock,  —  the  Americans  from 
their  English  ancestors,  —  than  the  more  perfect  and  durable  character 
of  all  their  mechanical  works,  machinery,  and  buildings.  There,  things 
are  made  to  endure ;  here,  they  are  made  to  answer  the  purposes  of  the 
day.  —  [Ed.  Farmer's  Library.} 


MATERIALS    OF    CONSTRUCTION.  101 

ship  may  be  little  experienced ;  but  where  the  structures  are 
large  and  extensive,  the  results  become  of  the  deepest  impor- 
tance, in  an  economical  point  of  view. 

It  is  not  easy  to  point  out  a  course  wherein  these  difficulties 
may  be  avoided,  or  to  discover,  at  all  times,  to  whom  blame  is 
attributable.  Tradesmen,  who  take  the  work  by  contract,  prob- 
ably endeavor  to  do  the  best  they  can  with  the  job  they  have 
taken  in  hand,  and  it  is  generally  their  policy  to  get  over  it  as 
easily  and  as  quickly  as  possible.  Gardeners  who  may  have 
the  superintendence  of  the  work,  probably  do  the§  best  they  can, 
but  from  their  wanting  the  necessary  knowledge  of  the  details 
of  construction,  are  unable  to  exercise^  that  surveJJlaric§  wfricji  is 
necessary  to  the  proper  execution  of  the.  \voik;  .„  :  ; J  :,„ ;  j^  f  Y> 

2.  Materials  of  the  Frame  of  the  Building,  fyc.  —  The  most 
suitable  material  for  the  frames  of  horticultural  buildings  has 
lately  been  made  the  subject  of  considerable  discussion  and  ex- 
periment, which  has  not  been  without  its  use  in  the  elucidation 
of  facts  hitherto  unknown,  or,  at  least,  unnoticed  in  general 
practice.  The  case  of  wood  versus  iron  has  been  investigated 
on  various  grounds,  by  practical  and  scientific  men,  without, 
however,  coming  to  a  unanimous  decision  on  the  superiority  of 
either.  In  this  matter,  as  in  some  others  like  itself,  some  have 
adopted  extreme  views  of  the  various  merits  and  defects  of  the 
different  materials,  and  have  come  to  their  conclusions  by  refer- 
ence to  some  single  or  specific  property.  These  views  and  con- 
clusions, however,  have  been  of  considerable  utility  in  bringing 
the  subject  before  the  bar  of  unbiased  inquiry,  which,  if  it  has 
not  already  done  so,  is  likely  to  result  in  the  adoption  of  modi- 
fied views,  and  the  recognition  of  specific  principles,  that,  when 
fully  considered  and  duly  weighed  against  each  other,  will  ulti- 
mately lead  to  a  more  definite  result. 

The  use  of  iron  in  the  construction  of  hot-houses,  like  every 
other  really  valuable  improvement,  has  met  with  much  opposi- 
tion from  the  still  slumbering  spirit  of  prejudice,  which  is  gener- 
ally slow  to  believe  in  the  superiority  of  anything  different  from 
that  with  which  it  has  been  long  acquainted,  even  when  this 
superiority  cannot,  on  reasonable  grounds,  be  denied.  This 


102  MATERIALS    OF    CONSTRUCTION. 

spirit,  however,  which  has  long  held  undisputed  sovereignty 
over  the  minds  of  gardeners,  is  fast  giving  way  before  the  sweep- 
ing current  of  mechanical  inventions ;  and  when  science  comes 
to  the  aid  of  mechanism  in  the  building  of  hot-houses,  as  in  the 
erection  of  factories,  steam-engines,  and  other  works  of  art,  then 
the  flimsy  barriers  reared  by  prejudice  will  be  swept  away,  and 
I  think  I  may  fearlessly  assert  that,  in  regard  to  the  opposition 
that  has  been  given  to  the  erection  of  iron  hot-houses,  this  has 
nearly  taken  place. 

Gardeners  ^from^  the  early  ages  of  Abercrombie  and  Nicol, 
h&ye}  been  Vjfregiarffced*  against  metallic  hot-houses,  and,  to  our 
knowledge, nfo\s  prejudice,  is  still  entertained  by  some  whose 
leyrbikng;azid^i'iit^fli^tiee-would  encourage  us  to  look  for  more 
accurate  judgment. 

The  objections  which  have  been  raised  against  metallic  houses 
for  horticultural  purposes,  are  chiefly  the  following :  — 

Contraction  and  expansion,  oxydation,  abduction  of  heat,  at- 
traction of  electricity,  and  original  cost. 

In  regard  to  the  first,  and  principal  cause  of  opposition,  viz., 
its  susceptibility  to  the  influences  of  heat  and  cold,  a  fact  which 
cannot  be  denied,  yet  it  is  proved  by  experience  that  if  a  house 
be  properly  constructed  of  good  material,  this  susceptibility  is 
of  no  practical  importance.  In  very  small  houses  the  incon- 
venience occasioned  by  sudden  fluctuations  of  temperature  may 
be  more  sensibly  felt,  although,  in  the  management  of  small  iron 
vineries,  in  England,  we  have  never  seen  the  slightest  incon- 
venience result  from  external  changes;  indeed,  all  our  expe- 
rience in  the  management  of  hot-houses  goes  to  prove  the 
superiority  of  iron  over  wood,  for  every  purpose  to  which  timber 
is  generally  applied.  It  has  been  stated  that  metallic  roofs  are 
more  liable  to  break  the  glass  than  wood  ;  practice  has  also 
proved  that  this  statement  is  without  foundation,  and  if  it  has 
ever  taken  place,  can  only  be  in  copper  or  compound  metallic 
roofs.  Cast-iron  or  solid  wrought-iron  bars  have  never  been 
known  to  cause  breakage  of  glass,  or  displacement  of  joints,  and 
some  have  asserted  that  the  breakage  of  glass  is  even  more, 
during  sudden  changes,  by  wood  than  by  iron  roofs. 

The  expansibility  of  copper  being  greater  than  that  of  iron, 


MATERIALS    OF    CONSTRUCTION.  103 

in  the  proportion  of  95  to  60,  therefore  copper  is  above  one  third 
more  likely  to  break  glass  than  iron.  But  when  it  is  considered 
that  a  rod  of  copper  expands  only  T^uVtftf  part  of  its  length  with 
every  degree  of  heat,  and  that  iron  only  expands  T^Vra  Part> 
the  practical  effects  of  even  the  hottest  portion  of  our  climate 
on  these  metals  can  never  amount  to  a  sum  equal  to  the  expan- 
sion required  for  the  breakage  of  glass. 

The  second  objection  which  we  have  mentioned  is  also  unde- 
niable. All  metals  are  liable  to  rust;  but  painting  easily  rids  us 
of  this  objection,  at  least  it  will  so  far  prevent  it  as  to  form 
hardly  any  objection. 

The  power  of  metals  to  conduct  heat  is  an  objection  which, 
like  the  others,  cannot  be  denied,  but  may  be  partially  obviated. 
The  abduction  of  heat,  like  the  expansibility  of  metallic  roofs, 
is  very  little  felt  in  using  them  ;  the  smaller  the  bars,  the  less 
their  power  of  conduction.  The  paint,  also,  and  the  putty  used 
to  retain  the  glass,  obviate  this  objection.  Heat  may  be  supplied 
by  art,  but  light,  the  grand  advantage  gained  by  metallic  bars, 
cannot,  by  any  human  means,  be  supplied  but  by  transparency 
of  roof. 

The  objection  raised  on  the  ground  of  attraction  of  electricity, 
is  easily  answered.  If  metallic  hot-houses  and  conservatories 
attract  electricity,  they  also  conduct  it  to  the  ground,  so  that  it 
can  do  them  no  harm.  What  is  corroborative  of  this  position 
is  the  fact,  that  no  instance  has  come  under  our  knowledge  of 
iron  hot-houses  having  been  injured  by  the  electric  fluid. 

The  objection  regarding  the  expense  of  iron  hot-houses,  has 
been  sufficiently  refuted  in  England,  and  we  have  observed, 
with  pleasure,  a  refutation  of  the  same  objection,  by  an  enter- 
prising gentleman  of  Cincinnati,  who  has  lately  erected  an  iron- 
roofed  vinery.  Mr.  Resorr  has  given  a  cut,  and  description  of 
this  house,  in  the  "  Horticulturist "  for  Sept.  1849,  p.  117.  This 
is  the  only  substantial  account  we  have  seen  of  the  comparative 
cost  of  iron  and  wood  roofs.  This  gentleman,  who  is  in  the 
foundery  business,  has  every  opportunity  of  knowing  the  accu- 
rate cost  of  such  a  house,  and  plainly  states,  "  that  those  wish- 
ing to  build  a  good,  substantial  house,  can  do  it,  and  make  the 
roof  of  iron,  as  cheaply  as  of  wood,  the  other  parts  costing  the 


104  MATERIALS    OF    CONSTRUCTION. 

same."  From  inquiries  and  calculations  which  we  have  made, 
we  have  come  to  the  same  conclusion,  although,  from  a  want 
of  the  requisite  knowledge,  and  from  the  expense  of  having 
patterns  made  for  the  castings,  it  may,  in  some  localities,  cost 
more  than  a  structure  of  wood. 

In  small  houses,  sudden  changes  of  the  external  temperature 
are  much  sooner  and  more  sensibly  felt  than  in  large  structures, 
whether  they  are  constructed  of  wood  or  iron,  which  arises  from 
the  fact  that  the  smaller  volume  of  air  confined  within  becomes 
more  rapidly  heated,  and  hence  the  change  is  the  sooner  felt. 
Supposing  the  circumstance  to  be  more  strikingly  sensible  in  the 
case  of  small  iron  houses,  —  then  all  that  is  necessary  to  coun- 
terbalance it,  is  just  a  little  more  attention  to  ventilation,  during 
sudden  changes  of  external  temperature. 

For  large  structures  iron  is  incomparably  superior  to  wood, 
and  even  for  forcing-houses  we  would  decidedly  prefer  the  same 
material.  The  contraction  and  expansion  of  metallic  hot-houses 
may  be  dreaded  in  the  Southern  States,  if  built  on  a  very  small 
scale,  and  badly  managed  ;  but  in  structures  of  moderate  size, 
this  evil  will  be  found  practically  of  little  importance,  unless 
they  are  badly  constructed,  and  negligently  managed. 

The  finest  horticultural  structures  that  have  yet  been  erected 
in  Europe  are  made  of  iron,  and  no  houses  of  any  importance 
are  now  being  erected  of  wood,  which  proves  its  superiority  over 
the  latter  material.  The  great  conservatory,  or  Palm-house, 
at  Kew,  is  wholly  of  iron,  constructed  under  the  auspices  of  the 
most  scientific  men  in  England.  The  Botanic  Society's  conser- 
vatory, in  the  Regent's  Park,  (already  spoken  of,)  is  made  of 
iron.  The  fine  plant-houses  in  the  Glasnevin  Botanic  Garden, 
near  Dublin,  are  constructed  of  iron,  and  the  quite  unequalled 
range  of  forcing-houses  at  Frogmore,  in  Windsor  Park,  are  also 
of  iron.  In  fact,  the  most  extensive  horticultural  erections  in 
Europe  are  made  of  iron,  and  many  others,  now  in  course  of 
erection,  are  being  made  of  the  same  material. 

Admitting  that  properly  constructed  iron  houses  would  cost, 
at  the  outset,  somewhat  more  than  wrooden  ones,  their  lightness 
and  elegance  render  them  much  superior  in  point  of  appearance, 
and,  when  their  durability  is  taken  into  consideration,  they  will, 


MATERIALS    OF    CONSTRUCTION.  105 

undoubtedly,  be  found  cheaper  in  the  end.  But  the  cost  of  con- 
struction will  vary,  according  as  the  details  are  understood  by 
the  constructors ;  for  if  Mr.  Resorr  can  make  a  vinery  of  iron  as 
cheaply  as  of  wood,  then  other  tradesmen,  when  they  have  prop- 
erly understood  the  nature  of  the  work,  will  surely  be  able  to 
do  the  same.  The  Palm-house  at  Kew  was  constructed  by  a 
tradesman  from  Dublin,  while  some  of  the  most  extensive  hot- 
house builders  in  England  lived  within  the  sound  of  their  ham- 
mers, and  the  material  and  workmen  were  all  brought  across  the 
channel,  costing  nearly  as  much  as  if  brought  to  America ;  yet 
the  workmanship  was  superior,  and  the  cost  said  to  be  less,  — 
proving  that  practice  and  knowledge  of  the  details  lessen  the 
original  cost  of  construction.* 

*  As  instances  of  comparatively  easy  transportability  of  iron  hot- 
houses, we  might  mention,  that  the  whole  of  the  materials  of  the 
immense  structure  at  Kew  were  manufactured  and  fitted  together  at 
Dublin,  and  transported  from  thence  to  London.  The  unequalled  range 
of  forcing-houses  at  Windsor,  one  thousand  feet  in  length,  was  made  at 
Birmingham,  and  fitted  together  in  the  works,  before  they  were  trans- 
ported to  their  final  destination.  Now  it  would  have  been  just  as  easy, 
and  perhaps  little  more  expensive,  to  have  shipped  them  to  New  York, 
or  Boston,  or  Philadelphia,  or  Baltimore.  When  this  is  done  in  England, 
how  long  will  American  enterprise  be  behind  them  ?  We  prophesy,  not 
long. 


SECTION    VI. 

GLASS. 

1.  EXPERIMENTS  which  have  hitherto  been  made,  in  regard  to 
the  physical  properties  of  glass  as  a  transparent  medium,  have 
been  conducted,  generally,  on  purely  chemical  principles,  and 
mostly  without  reference  to  observed  facts,  as  regards  the  growth 
of  plants,  excepting,  perhaps,  those  of  the  most  common  and 
obvious  character.  Partly  for  this  reason,  and  partly  from  care- 
less negligence,  hot-houses  have  long  been,  and  still  continue 
to  be,  glazed  with  material  of  a  very  inferior  description.  If 
any  one  doubts  this,  let  him  look  at  some  of  the  finest  hot- 
houses in  the  country,  and  he  will  easily  perceive  the  truth  of 
this  statement ;  the  sickly  and  scorched  appearance  of  the 
plants  under  its  influence,  being  far  more  painful  than  agreeable 
to  the  eye  of  any  one  who  takes  an  interest  in  the  vegetable 
kingdom.  This  evil,  alone,  renders  the  very  best  cultivation  of 
no  avail. 

The  most  elaborate  and  practically  useful  investigations  that 
have  yftt  been  made,  in  this  department,  are  those  lately  under- 
taken, with  the  view  of  securing  the  very  best  material  that 
science  and  art  could  produce,  for  the  glazing  of  the  great  Palm- 
house  at  Kew.  We  cannot  do  better  than  present  our  readers 
with  the  following  extract  from  Mr.  Hunt's  report  to  the  com- 
mittee, which  we  take  from  Silliman's  Journal  of  Science  and 
Art,  vol.  iv.,  p.  431. 

"  It  has  been  found  that  plants  growing  in  stove-houses,  often 
suffer  from  the  scorching  influence  of  the  solar  rays,  and  great 
expense  is  frequently  incurred,  in  fixing  blinds,  to  cut  off  this 
destructive  calorific  influence.  From  the  enormous  size  of  the 
new  Palm-house,  at  Kew,  it  would  be  almost  impracticable  to 
adopt  any  system  of  shades  that  would  be  effective,  this  building 
being  363  feet  in  length,  100  feet  wide,  and  63  feet  high.  It 


GLASS.  107 

was,  therefore,  thought  desirable  to  ascertain  if  it  would  be  pos- 
sible to  cut  off  these  scorching  rays  by  the  use  of  a  tinted  glass, 
which  should  not  be  objectionable  in  its  appearance,  and  the  ques- 
tion was,  at  the  recommendation  of  Sir  William  Hooker  and 
Dr.  Lindley,  submitted,  by  the  commissioners  of  woods,  &c.,  to 
Mr.  Hunt.  The  object  was  to  select  a  glass  which  should  not 
permit  those  heat  rays,  which  are  most  active  in  scorching  the 
leaves  of  plants,  to  permeate  it.  By  a  series  of  experiments,  made 
with  the  colored  juices  of  the  palms  themselves,  it  was  ascer- 
tained that  the  rays  which  destroyed  their  color  belonged  to  a 
class  situated  at  the  end  of  the  prismatic  spectrum,  which  ex- 
hibited the  utmost  calorific  power,  and  just  beyond  the  limits  of 
the  visible  red  ray.  A  great  number  of  specimens  of  glass,  vari- 
ously manufactured,  were  submitted  to  examination,  and  it  was 
at  length  ascertained,  that  glass  tinted  green  appeared  most  likely 
to  effect  the  object  desired,  most  readily.  Some  of  the  green 
glasses  that  were  examined,  obstructed  nearly  all  the  heat  rays  ; 
but  this  was  not  desired,  and,  from  their  dark  color,  these  were 
objectionable,  as  stopping  the  passage  of  a  considerable  quantity 
of  light,  which  was  essential  to  the  healthy  growth  of  the  plants. 
Many  specimens  were  manufactured  purposely  for  the  experi- 
ments, by  Messrs.  Chance,  of  Birmingham,  according  to  given 
directions ;  and  it  is  mainly  due  to  the  interest  taken  by  these 
gentlemen,  that  the  desideratum  has  been  arrived  at. 

"  Every  sample  of  glass  was  submitted  to  three  distinct  sets  of 
experiments. 

"  First.  —  To  ascertain,  by  measuring  off  the  colored  rays  of 
the  spectrum,  its  transparency  to  luminous  influence. 

"  Second.  —  To  ascertain  the  amount  of  obstruction  offered  to 
the  passage  of  the  chemical  rays. 

"  Third.  —  To  measure  the  amount  of  heat  radiation  which 
permeated  each  specimen. 

"  The  chemical  changes  were  tried  upon  chloride  of  silver,  and 
on  papers,  stained  with  the  green  coloring  matter  of  the  leaves 
of  the  palms  themselves.  The  calorific  influence  was  ascer- 
tained by  a  method  employed  by  Sir  John  Herschel,  in  his  ex- 
periments on  solar  radiation.  Tissue  paper  was  smoked  on  one 
side,  by  holding  it  over  a  smoky  flame,  and  then,  while  the 
10 


108 


GLASS. 


spectrum  was  thrown  upon  it,  the  other  surface  was  washed 
with  strong  sulphuric  ether.  By  the  evaporation  of  the  ether, 
the  points  of  calorific  action  were  most  easily  obtained,  as  these 
dried  off  in  well  defined  circles,  long  before  the  other  parts  pre- 
sented any  appearance  of  dryness.  By  these  means  it  is  not 
difficult,  with  ease,  to  ascertain  exactly  the  conditions  of  the 
glass,  as  to  its  transparency  to  light,  heat,  and  chemical  agency, 
(actinism.) 

"  The  glass  thus  chosen  is  of  a  very  pale  yellow  green  color, 
the  color  being  given  by  oxide  of  copper,  and  is  so  transparent 
that  scarcely  any  light  is  intercepted.  In  examining  the  spec- 
tral rays  through  it,  it  is  found  that  the  yellow  is  slightly  dimin- 
ished in  intensity,  and  that  the  extent  of  the  red  ray  is  diminished 
in  a  small  degree,  the  lower  edge  of  the  ordinary  red  ray  being 
cut  off  by  it.  It  does  not  appear  to  act  in  any  way  upon  the 
chemical  principle,  as  spectral  impressions,  obtained  upon  chlo- 
ride of  silver,  are  the  same  in  extent  and  character  as  those 
procured  by  the  action  of  the  rays  which  have  passed  ordinary 
white  glass.  This  glass  has,  however,  a  very  remarkable  action 
upon  the  non-luminous  heat  rays,  the  least  refrangible  calo- 
rific rays.  It  prevents  the  permeation  of  all  that  class  of  heat 
rays  which  exists  below,  and  in  the  point  fixed  by  Sir  William 
Herschel,  Sir  H.  Englefield,  and  Sir  J.  Herschel,  as  the  point 
of  maximum  calorific  action,  and  it  is  to  this  class  of  rays  that 
the  scorching  influence  is  due.  There  is  every  reason  to  con- 
clude that  the  use  of  this  glass  will  be  effectual  in  preserving 
the  plants,  and  at  the  same  time  that  it  is  unobjectionable  in  point 
of  color,  and  transparent  to  that  principle  which  is  necessary  for 
the  development  of  those  parts  of  the  plant  which  depend  upon 
external  chemical  excitation,  it  is  only  partially  so  to  the  heat 
rays,  and  it  is  opaque  to  those  only  that  are  injurious.  The 
absence  of  the  oxide  of  manganese,  commonly  employed  in  all 
sheet  glass,  is  insisted  on,  it  having  been  found  that  glass,  into 
the  composition  of  which  manganese  enters,  will,  after  exposure 
for  some  time  to  intense  sun-light,  assume  a  pink  hue,  and  any 
tint  of  this  character  would  completely  destroy  the  peculiar 
properties  for  which  this  glass  is  chosen.  Melloni,  in  his  in- 
vestigations on  radiant  heat,  discovered  that  a  peculiar  green 


GLASS. 

glass  manufactured  in  Italy,  obstructed  nearly  all  the  calorific 
rays.  We  may,  therefore,  conclude  that  the  glass  chosen  is  of 
a  similar  character  to  that  employed  by  the  Italian  philosopher. 
The  tint  of  color  is  not  very  different  from  that  of  the  old  crown 
glass,  and  many  practical  men  state,  that  they  find  their  plants 
flourish  better  under  this  kind  of  glass,  than  under  the  white 
sheet  glass,  which  is  now  so  commonly  employed." 

We  understand  the  glass  employed  in  the  Kew  Palm-house 
has  fully  answered  the  intended  purpose,  viz.,  of  obstructing  the 
most  injurious  portion  of  the  heat  rays;  and  we  have  learned, 
also,  that  it  has  answered  all  expectations  as  to  its  influence  on 
the  health  of  the  plants,  although  its  perfect  utility,  in  this 
respect,  has  been  doubted  by  some  practical  men.  We  think, 
however,  that  an  absolute  decision  on  its  merits,  in  this  respect, 
is  rather  premature,  as  we  should  prefer  seeing  the  plants  attain 
a  greater  size,  so  as  to  fill  the  structure  more  completely,  and 
their  foliage  reach  nearer  to  the  glass,  before  pronouncing  defi- 
nitely upon  the  calorific  effects  of  the  latter. 

As  to  the  appearance  of  this  glass,  it  is  altogether  a  matter 
of  taste,  which  we  consider  ourselves  having  no  right  to  ques- 
tion ;  and,  upon  the  whole,  we  think  it  in  this  respect  unob- 
jectionable. When  viewed  obliquely,  from  a  distance,  it  is 
slightly  gr&en,  but  when  viewed  from  within,  and  at  right 
angles  to  its  surface,  it  is  clear  and  nearly  white.  This  kind 
of  glass  is  highly  worthy  of  the  attention  of  glass-makers  and 
horticulturists  in  this  country,  and  we  have  no  doubt,  when  its 
qualities  have  been  fairly  tested  and  made  known,  it  will  be 
extensively  employed  in  horticultural  buildings. 

No  kind  of  economy  is  more  sure  to  defeat  its  end  than 
using  cheap  glass  in  horticultural  structures.  Many  suppose, 
if  a  house  is  merely  covered  with  glass  and  made  transparent, 
that  all  is  well.  We  know  this  to  be  a  common  opinion ;  yet 
we  are  fully  prepared  to  prove  its  falsity,  not  by  mere  assertion, 
but  by  indubitable  facts,  —  facts  so  clear  that  the  most  ignorant 
in  these  matters  will  be  convinced,  from  his  own  observation, 
and  on  a  scale  so  extensive,  as  to  justify  the  conclusions  that 
have  been  drawn  from  them. 

We  know  of  nothing  connected  with  the  erection  of  horticul- 


110  GLASS. 

tural  buildings  so  vexatious  as  having  the  roof  glazed  with, 
bad  glass ;  plants  of  almost  every  kind  are  certain  to  suffer 
under  it.  Knotted  and  wavy  glass  is  the  worst  of  all,  as  the 
knots  and  waves  form  lenses,  and  concentrate  the  sun's  rays 
upon  the  plants,  and  that  part  on  which  the  concentrated  ray 
falls  is  sure  to  be  burnt.  It  cannot  for  one  moment  be  doubted 
that  the  glass  used  in  the  majority  of  horticultural  buildings  is 
not  only  inferior,  but  is  of  the  very  worst  description ;  and,  on  a 
recent  examination  of  one  hundred  houses,  we  found  scarcely 
one  free  from  the  defects  here  spoken  of.  Indeed,  we  are  fully 
aware  of  the  difficulty  of  procuring  really  good  glass,  at  reasona- 
ble prices,  for  glazing  hot-houses.  But  there  cannot  be  a  doubt 
that  the  money  saved  is  money  lost ;  and  if  the  vexation  and 
annoyance  subsequently  incurred  by  the  use  of  inferior  glass,  be 
taken  into  consideration,  few  persons  of  sound  judgment  will 
hesitate  in  paying  an  increased  price. 

No  doubt  many  of  our  readers  will  suppose  that  we  are 
unnecessarily  particular  on  this  point,  but  our  experience  has 
taught  us  a  severe  lesson,  and  one,  too,  which  no  doubt  has 
been  strongly  impressed  upon  the  mind  of  every  gardener,  of 
lengthened  experience  in  these  matters.  Against  such  an  evil 
there  is  but  one  resource,  —  and  a  bad  one  it  is,  —  which  is 
shading,  either  by  means  of  cloth  blinds,  or  by  painting,  the 
worst  method  of  the  two;  but  the  one  or  the  other  is  absolutely 
necessary.  The  first  is  troublesome,  the  other  is  unsightly; 
and,  to  be  done  right,  both  are  expensive.  We  have  a  large 
house  now  under  our  management,  on  which  the  glass  is  so  bad 
as  to  render  its  opacity  absolutely  necessary  to  prevent  burning, 
even  when  the  sun's  rays  have  lost  their  meridian  power. 

In  very  small  houses  bad  glass  may  be  used  with  less  chance 
of  injury,  as  they  may  be  easily  shaded  with  blinds  during  the 
noonday  sun ;  but  in  very  large  structures  this  is  only  accom- 
plished at  very  great  expense ;  and  in  curvilinear  houses,  and 
houses  with  irregular  roofs,  covering  them  with  blinds  is  almost 
impossible.  Painting  the  glass,  then,  is  the  only  resource, 
unless  glass  be  used  which  does  not  require  it. 

Little  has  been  said  on  the  effects  of  glass  used  in  hot-houses, 
by  writers  on  practical  horticulture.  Although  facts  are  obvious 


GLASS.  Ill 

and  familiar  in  regard  to  it,  yet  the  evils  seem  to  be  passed  over 
as  results  which  cannot  be  prevented.  We  can  at  this  moment 
point  to  houses  standing  side  by  side,  in  one  of  which  it  is 
impossible  to  grow,  and  keep  in  health,  any  species  of  vegeta- 
tion whatever,  —  no  matter  how  hardy  the  tissue  of  the  foliage 
may  be,  —  without  shading  the  glass  almost  to  opacity ;  while, in 
the  other,  plants  with  tender  and  delicate  foliage  stand  compar- 
atively uninjured.  The  cause  is  obvious :  the  glass  with  which 
the  one  is  glazed  is  full  of  waves  and  blotches,  and  altogether 
of  the  worst  description ;  while  that  of  the  other,  though  not  the 
best,  is  yet  of  better  quality.  The  poorer  glass  burns  vegetation, 
even  when  the  incidental  angle,  between  the  impinging  ray  and 
a  perpendicular  to  the  roof,  is  as  much  as  45°. 

From  what  has  been  already  said  regarding  the  influence  of 
the  different  solar  rays  on  vegetation,  and,  more  especially,  the 
experiments  made  with  regard  to  the  Palm-house  at  Kew  Gar- 
dens, by  which  it  has  been  found  possible  to  manufacture  glass 
which  is  opaque  to  the  scorching  rays,  without  at  the  same  time 
obstructing  the  light,  heat,  and  chemical  rays  which  are  essen- 
tial to  the  development  of  plants,  there  can  be  no  doubt  that 
the  scorching  of  vegetation  in  hot-houses,  which  has  long  been 
a  serious  drawback  in  exotic  horticulture,  can  be  prevented. 
And  when  more  extended  experiments  have  been  made,  a  good 
material  for  glazing  can  undoubtedly  be  manufactured  at  a  price 
that  will  insure  its  universal  adoption  in  horticultural  structures. 
It  is  to  be  earnestly  desired  that  some  of  our  enterprising  manu- 
facturers, —  a  class  so  remarkable  for  their  fertility  of  invention, 
—  will  take  up  the  matter  seriously,  and  supply  us  with  the 
material  which  exotic  horticulture  so  much  requires. 

2.  Glazing.  —  Common  sash-glazing  is  generally  performed 
with  a  lap  of  from  one  to  three  fourths  of  an  inch,  and,  by  many, 
with  a  full  inch  lap.  This  is  a  most  objectionable  method,  as 
the  broader  the  lap  the  greater  the  quantity  of  water  retained 
in  it  by  capillary  attraction,  and,  consequently,  the  greater  the 
breakage  of  the  glass ;  for  when  the  internal  temperature  falls, 
and  this  water  becomes  frozen,  the  glass  is  certain  to  crack  in 
the  direction  of  the  bars.  The  lap  should  never  be  broader  than 
10* 


112  GLASS. 

a  quarter  of  an  inch,  but  where  the  panes  or  pieces  of  glass  are 
not  above  five  inches  wide,  one  eighth  of  an  inch  is  sufficient. 
Half  an  inch  in  roof-sashes,  unless  they  are  placed  at  an  angle 
of  not  less  than  45°,  is  almost  sure  to  produce  breakage,  except- 
ing the  temperature  within  be  kept  sufficiently  high  to  prevent 
the  water  retained  between  the  panes  from  freezing. 

Broad  laps  are  objectionable,  also,  on  other  accounts ;  for  the 
broader  the  lap  the  sooner  it  fills  with  earthy  matter,  forming 
an  opaque  space,  and  these  spaces  are  so  numerous  as  to  have 
a  very  considerable  effect  upon  the  transparency  of  the  roof, 
which  is  injurious  by  excluding  the  light,  and  is  also  unsightly 
in  appearance.  It  may  be  puttied,  but  its  opacity  is  the  same, 
and  its  appearance  no  better  than  if  filled  with  dirt.  Where 
the  lap  is  not  more  than  one  fourth  of  an  inch,  it  may  be  puttied 
without  any  very  disagreeable  effect,  but  if  the  glass  be  per- 
fectly smooth  in  the  edges,  puttying  is  useless,  and  the  glass  is 
better  without  it. 

The  most  approved  practice  as  to  the  laps,  whether  in  roofs 
or  common  sashes,  is,  to  make  the  breadth  of  the  lap  equal  to 
the  thickness  of  the  glass,  leaving  it  entirely  without  putty. 
But  it  is  extremely  difficult  to  get  glaziers  to  attend  to  this,  and 
it  can  only  be  obtained  by  employing  good  workmen,  and  keep- 
ing strict  supervision  over  the  work.  This  is  not  only  the  most 
elegant  of  all  modes  of  glazing,  but  the  safest  for  the  glass, 
which,  as  we  have  observed,  is  seldom  broken  by  any  other  nat- 
ural means  but  the  expansion  of  frozen  water  retained  between 
the  laps.  This  mode  is  also  by  far  the  easiest  to  repair,  and  is 
more  durable  than  any  method  of  filling  the  laps  with  putty,  or 
with  lead. 

There  are  various  other  modes  of  glazing,  as  the  lead  and 
oopper-lap  methods,  which,  however,  are  so  very  objectionable 
as  to  be  unworthy  of  occupying  space  in  our  description.  The 
methods  of  shield  glazing  are  equally  objectionable,  and  little 
used.  Curvilinear  glazing  has  been  used  somewhat  extensively, 
and  is,  in  the  opinion  of  some  men  of  undoubted  skill,  superior 
to  the  other  methods  already  spoken  of. 

Curvilinear  lap-glazing  appears  preferable  to  the  square  mode, 
for  various  reasons,  one  of  which  is,  that  the  curve  has  a  ten- 


GLASS.  113 

dency  to  conduct  the  water  to  the  centre  of  the  pane,  which  is 
let  out  by  a  small  opening  at  the  apex  of  it.  If  the  lap  is  broad, 
however,  the  water  is  accumulated  by  attraction  precisely  in  the 
point  where  it  is  calculated  to  do  most  injury,  —  acting,  in  fact, 
as  a  power  on  the  end  of  two  levers  of  the  second  kind.  But 
when  the  lap  is  not  more  than  one  sixteenth  of  an  inch  in  width, 
no  evil  of  this  sort  can  happen. 

It  ought  to  be  borne  in  mind  that  puttying,  or  otherwise  fill- 
ing up  the  laps,  is  in  no  case  necessary  if  care  be  taken  of  the 
glazing,  and  smooth  glass  be  used,  and  if  the  lap  never  exceeds 
one  fourth,  nor  falls  short  one  sixteenth,  of  an  inch.  However 
careful  the  laps  may  be  puttied,  in  a  very  few  years  the  putty 
begins  to  decay  by  absorption  of  moisture,  and,  when  evapora- 
tion is  great  within,  it  becomes  saturated  with  water,  which 
readily  freezes  in  frosty  nights,  (unless  the  temperature  of  the 
house  is  adequate  to  prevent  it,)  and  breakage  of  glass  is  inevi- 
table. 

Reversed  curvilinear  glazing  consists  in  making  the  lower 
edges  of  the  panes  to  curve  inwards,  in  a  concave  form,  instead 
of  curving  outwards,  in  the  common  way.  The  effect  of  this 
method  is  the  throwing  of  the  condensed  moisture  down  upon 
the  bars,  and  thus  conveying  it  off  at  the  bottom  of  the  roof, 
which  prevents  the  moisture  from  being  retained  in  globules, 
and  dropping  down  upon  the  plants.  This  method  is  nothing 
more  than  reversing  the  position  of  the  panes  in  common  curvi- 
linear glazing,  and  is,  according  to  our  opinion,  preferable  to  it. 

These  are  the  most  common  and  approved  modes  of  glazing, 
although  some  others  have  been  used  that  have  not  proved 
worthy  of  general  adoption.  Ridge-and-furrow  roofs  may  be 
glazed  in  the  same  way.  The  size  of  the  panes  used  makes  no 
difference,  —  large  ones  only  tending  to  reduce  the  opaque  sur- 
face. Anomalous  surfaces  may  be  glazed  with  panes  according 
to  the  figures  of  the  bars. 

. 

3.  Color  of  Walls.  —  The  color  usually  applied  to  hot-houses 
is  white.  As  affording  the  finest  contrast  with  the  plants  in  the 
interior,  and  the  vegetation  around  the  outside  of  the  house,  the 
general  taste  is  manifestly  in  favor  of  this  color;  and,  as  it  is 


114 


GLASS. 


the  best  reflector  of  light,  it  is,  also,  on  that  account,  preferable 
to  any  other.  There  are  some  considerations,  however,  in  favor 
of  a  dark  color,  which,  as  has  been  already  stated,  absorbs  a 
larger  quantity  of  heat,  and  parts  with  it  again  on  the  cooling 
of  the  atmosphere.  A  yellow  color  we  consider  the  most  objec- 
tionable of  all,  both  on  account  of  its  contrasting  badly  with  the 
glass  of  the  house  and  the  verdure  of  vegetation,  as  well  as  the 
effects  produced  by  it  on  the  light,  which,  as  will  be  seen  from 
the  preceding  investigations,  exercises  an  injurious  influence  on 
vegetation.  The  influence  may  not  be  so  great  in  the  reflected 
light,  as  when  permeating  yellow  or  orange-colored  media,  but 
the  power  is,  nevertheless,  exercised  to  some  extent.  The  same 
investigations  show  the  beneficial  influence  of  a  blue,  or  dark 
color,  which  perfectly  accords  with  our  observations  on  plants 
growing  against  dark  bodies,  otherwise  exposed  to  abundance 
of  light;  and,  when  it  is  in  accordance  with  the  taste  of  the 
proprietor,  we  think  the  interior  walls  of  hot-houses  should  be 
of  a  dark  color. 

In  England,  where  the  rays  of  light  are  less  powerful  than 
here,  dark-colored  walls  are  now  very  common.  There,  light  is 
a  more  important  consideration  than  heat :  the  latter  can  be 
applied  by  artificial  means ;  —  not  so  the  former.  This  probably 
tends  to  prevent  the  adoption  of  a  dark  color  for  the  interior  of 
their  hot-houses.  Here,  dark  walls  are  more  desirable  than 
white,  as  they  absorb  the  heat-rays,  during  a  powerful  sun,  and 
prevent  the  atmosphere  from  becoming  so  rapidly  hot.  This 
fact  is  sensibly  felt  on  standing  before  walls  of  the  different 
colors  during  the  mid-day  sun.  By  a  white  wall,  the  rays  are 
reflected  from  the  wall  back  into  the  air,  or  on  any  other  body 
which  is  near  it,  by  which  the  temperature  of  the  air  and  the 
body  is  very  much  increased.  A  dark-colored  wall,  on  the  con- 
trary, retains  the  heat  which  falls  on  its  surface ;  and  though  it 
may  feel  colder,  it  contains  more  latent  heat,  which  it  only  parts 
with  when  it  is  abstracted  by  the  reduced  temperature  of  the 
atmosphere.  This,  alone,  is  a  good  argument  in  favor  of  dark- 
colored  walls  in  lean-to  hot-houses. 

The  inner  side  of  the  rafters,  astragals,  and  sash-bars,  should 
approach  to  the  color  of  the  glass.  As  the  light-rays  do  not 


GLASS.  115 

fall  on  them,  nothing  is  gained  by  making  them  dark,  and  it 
gives  the  house  a  heavy  and  gloomy  effect.  The  structure  is, 
or  should  be,  transparent.  The  impression  on  the  mind  is 
that  of  a  house  covered  with  glass;  and,  as  the  rafters  and 
astragals  are  only  there  as  supports  to  the  glass,  they  should  be 
-deprived,  as  much  as  possible,  of  their  opaque  character.  When 
they  are  painted  a  dark  color,  the  reverse  effect  is  produced.  A 
glaring  white  color  is,  also,  objectionable  ;  it  is  hurtful  to  the 
eye,  and  generally  displeasing  to  a  refined  taste  :  some  of  the 
different  shades  of  cream,  or  light  stone  color,  will  be  more 
effective  and  pleasing.  The  same  may  be  said  in  regard  to  the 
external  portions  of  the  roof.  It  may,  by  way  of  contrast,  be  a 
shade  or  two  darker  than  the  interior;  but  a  decidedly  dark 
color  should  be  avoided.  We  have  seen  various  plant-houses 
painted  dark,  and  even  dark  red,  but  have  seen  very  few  who 
admired  them.  We  do  not  wish  to  incur  censure  by  finding 
fault  with  the  taste  of  those  who  may  fancy  these  colors,  and 
admit  that  every  one  has  an  undoubted  right  to  gratify  his 
own  taste.  We  give  our  opinions  for  the  benefit  of  those  who 
may  choose  to  adopt  them. 

It  is  a  good  plan  to  give  the  wood-work  of  the  structure  a 
coat  of  some  anti-corrosive  paint  before  the  color  is  put  on.  The 
timber  is  preserved  much  longer ;  and  the  house  requires  less 
painting,  as  the  timber  is  hardened,  and  more  impervious  to 
moisture.  For  numerous  preservative  solutions,  see  Table 
XVIII,  Appendix. 


SECTION    VII. 

FORMATION      OF     GARDENS. 

1.  Form  of  the  Garden.  —  The  form  of  the  garden  must  be 
determined  by  two  conditions :   first,  the  natural  disposition  of 
the  ground  chosen  for  its  site  ;  and,  secondly,  by  the  aspect  and 
position  of  the  walls  and  hot-houses.     If  there  are  no  hot-houses 
or  walls,  the  form  of  the  garden  will  be  regulated  mainly  by  the 
first  condition.     In  most  kitchen  or  culinary  gardens,  of  any 
importance,  if  no  walls  are  erected,  wooden  palings  are  generally 
substituted  for  them,  which  also  regulate  the  disposition  of  the 
ground.     The  site  having  been  fixed  upon,  with  due  regard  to 
the  considerations  necessary  in  choosing  the  site  for  horticultu- 
ral structures,  (see  Sect.  I,)  these  considerations  being  in  both 
cases  equally  applicable,  the  next  thing  to  be  done  is  the  dispo- 
sition and  formation  of  the  walks,  which  also  define  the  size 
and  shape  of  the  borders  and  principal  compartments  of  the 
garden. 

2.  Walks. — The  principal  walks  from  the   house   to   the 
garden  should  be  somewhat  broader  than  the  garden  walks,  and 
should,  if  possible,  enter  the  garden  at  the  south  side.     This  is 
more  especially  desirable  if  there  be  hot-houses  on  the  south 
side.     In  either  case,  however,  it  is  desirable,  as  a  more  favor- 
able impression  is  produced  on  the  mind  of  the  spectator  than  if 
entering  at  either  side.     The  north  side  is  the  very  worst  for 
the  principal  entrance,  as' the  necessary  offices  connected  with 
the  garden,  —  the  mould-heaps,  rubbish-piles,  manure,  &c., — 
are  generally  located  in  that  quarter ;  besides,  the  impression, 
produced  by  the  best  trained  trees  on  the  walls  or  fences,  and 
the  general  view  of  the  ground,  is  lost.     Next  to  the  south,  the 
east  or  west  sides  should  be  chosen. 

There  are  various  methods  of  forming  walks,  according  to  the 


FORMATION    OF    GARDENS.  117 

character  of  the  soil  and  sub-soil,  and  the  kind  of  material  at 
hand  to  form  a  surface.  Where  the  ground  is  naturally  wet,  or 
where  there  is  a  liability  of  the  accumulation  of  water,  the  soil 
should  be  taken  out  to  the  depth  of  at  least  twenty  inches,  — 
the  section  formed  by  the  excavation  forming  an  obtuse  angle 
towards  the  centre,  or  forming  the  segment  of  a  circle.  These 
excavations  should  lead  into  drains,  at  the  lowest  points,  to  carry 
off  the  water  that  percolates  through  among  the  stones  with 
which  they  are  filled.  They  may  be  filled  to  within  two  inches 
of  the  intended  surface  of  the  walk,  —  the  largest  in  the  bottom, 
and  the  smaller  toward  the  surface.  This  forms  a  durable  arid 
dry  walk  at  all  seasons ;  and,  where  the  soil  contains  a  consid- 
erable quantity  of  stones,  which  have  been  thrown  out  in  the 
process  of  trenching,  or  the  rubbish  of  building-materials,  this 
affords  a  good  medium  of  getting  them  out  of  the  way. 

On  dry,  gravelly  ground,  however,  these  excavations  are  use- 
less, so  far  as  drainage  is  concerned ;  and,  shovelling  aside  the 
mere  surface-soil,  the  walk  may  be  laid  down  on  the  substratum 
beneath  it.  If  the  walks  are  on  a  level,  or  nearly  so,  the  water 
generally  finds  its  way  off  as  quickly  as  it  falls,  and  the  cost  of 
excavation  is  saved. 

The  surface  of  walks  may  be  formed  of  grass,  gravel,  or  sand. 
Good  gravel  is  the  best,  sand  the  very  worst,  and  grass  can  only 
be  introduced  with  propriety  in  particular  places.  Sand,  or 
loose  gravel,  makes  a  very  uncomfortable  walk,  and,  when  of 
great  length,  is  tiresome  and  disagreeable  to  walk  upon. 

A  very  common  error,  among  those  not  acquainted  with  the 
proper  method  of  making  walks,  is,  to  lay  on  too  much  surface- 
material;  and,  in  many  places,  we  have  seen  trenches  taken 
out  for  walks,  and  filled,  to  the  depth  of  a  foot  or  more,  with 
gravel,  which,  if  laid  on  a  hard  surface  to  the  depth  of  an  inch 
or  less,  would  have  made  a  good  walk,  but.  which,  at  such  a 
depth,  all  the  walking,  rolling,  and  pressing  of  years  could  never 
make  it  bind.  It  requires  more  skill  than  is  generally  supposed 
to  make  good  walks.  Among  all  the  operations  of  the  garden- 
maker  there  is  scarcely  one  which  we  are  so  much  disposed  to 
find  fault  with,  as  in  the  making  of  walks  ;  and  this  is  precisely 

•»  -'  •• 


118  FORMATION  OF  GARDENS. 

our  reason  for  adverting  to  a  matter  which  is  apparently  irrele- 
vant to  the  general  character  of  the  present  work. 

The  durability  and  comfort  of  walks  consist  chiefly  in  their 
power  of  resisting  the  action  of  the  feet  in  walking  on  them,  at 
all  seasons  of  the  year.  Soft  gravel  walks,  that  yield  no  resist- 
ance to  the  motion  of  the  body,  are  obviously  unfit  for  being  in 
a  place  where  frequent  walking  is  resorted  to.  Sand,  also, 
makes  a  pretty  walk  to  look  at,  but  should  never  be  employed 
where  a  good  hard  walk  is  required,  unless  it  naturally  pos- 
sesses the  property  of  binding. 

It  is  quite  possible,  however,  to  have  a  hard  solid  walk,  capa- 
ble of  resisting  the  action  of  the  feet,  and  yet  appear  to  have  a 
gravelly  or  sandy  surface,  which  is  frequently  admired.  This 
is  effected  by  preparing  the  lower  strata  of  open  material,  then 
a  substratum  of  binding  material,  and  lastly,  a  thin  layer  of 
whatever  material  is  wished  for  the  surface,  which  should  be 
sifted  before  being  laid  on.  It  is  then  well  watered,  if  dry; 
then  rolled  well  in,  which  has  the  effect  of  mixing  it  with  the 
binding  stratum  beneath,  and  leaving  a  smooth  surface,  that 
becomes  harder  the  longer  it  is  used.  In  making  up  the  sub- 
strata, it  is  necessary  to  tread  each  layer  firmly  as  it  is  made 
up,  so  that  no  hollows  or  inequalities  may  occur  on  its  subsida- 
tion,  and  subsequent  use. 

It  must  be  remembered  that  the  material  of  which  the  surface 
of  a  walk  is  composed,  will  not  bind  by  any  mechanical  means, 
unless  it  contains  something  of  a  binding  nature  within  itself. 
Clean  gravel  will  not  bind  by  any  degree  of  mechanical  pres- 
sure, unless  it  contains  something  to  induce  a  general  compact- 
ness and  solidity  over  the  w-hole  surface. 

The  best  material  which  we  have  met  with  in  this  country, 
and  which  is  no  doubt  abundant  in  many  places,  is  a  kind  of 
soft  decomposing  sandstone  rock,  containing  a  large  quantity  of 
oxide  of  iron.  It  must  be  laid  down  where  it  is  finally  to 
remain,  when  newly  taken  out  of  the  pit,  then  subjected  to  a 
good  shower  of  rain,  or  watered,  and  afterwards  rolled  or  well 
trodden  with  the  feet ;  it  makes  a  solid  walk,  nearly  as  compact 
as  the  rock  itself.  It  may  be  objectionable  on  account  of  its 


FORMATION  OF  GARDENS.  119 

color,  but  this  is  easily  changed  by  a  thin  layer  of  any  other 
material  on  its  surface,  which  partly  mixes  and  binds  with  it. 

Broken,  or  what  is  sometimes  called  rotten  rock,  containing 
oxide  of  iron,  is  to  be  preferred  to  gravel  for  making  a  surface, 
and  pit  gravel  is  to  be  preferred  to  river  or  sea  gravel,  as  it  con- 
tains generally  more  oxide  and  earthy  matter.  Clay  forms  a 
good  under-surface,  and  when  thinly  covered  with  small  gravel 
and  well  rolled,  forms  a  most  excellent  and  durable  walk. 
Common  gravel  may  also  be  mixed  with  coal  ashes  and  lime 
rubbish,  which  tends  to  bind  it,  and  also  with  common  garden 
soil ;  but  this  is  a  last  resource.  Gravel  mixed  with  earth,  and 
more  especially  vegetable  earths,  has  a  great  tendency  to  pro- 
duce weeds,  and  is  therefore  very  troublesome  to  keep  clean. 
It  also  readily  absorbs  moisture  and  becomes  soft  in  wet  weather, 
and  especially  during  winter  frosts. 

Where  expense  is  not  spared,  a  composition  may  be  made, 
consisting  of  small  shell  gravel,  or  pounded  granite,  about  one 
tenth  part  of  brick-dust,  and  cement,  mixed  together.  This,  laid 
down  upon  a  firm,  prepared  surface,  in  a  wet  state,  and  well 
rolled,  will  form  a  surface  as  hard  as  marble. 

The  form  of  the  surface  should  be  nearly  flat ;  grass  walks 
should  be  completely  so ;  gravel  walks  may  rise  slightly  towards 
the  middle,  but  not  so  much  as  to  affect  the  convenience  of  as 
many  persons  walking  abreast  as  the  breadth  of  the  walk  will 
admit.  A  walk  six  or  eight  feet  wide  should  not  fall  more  than 
an  inch  towards  each  side,  this  being  sufficient  to  throw  the 
water  that  falls  on  it  towards  each  side,  without  being  any 
inconvenience  to  pedestrians  occupying  its  whole  breadth. 

If  the  walk  be  edged  with  turf,  the  crown  of  the  walk  should, 
when  finished,  be  on  a  level  with  the  turf  at  each  side,  one  inch 
being  quite  enough  for  depth  of  edging ;  besides,  the  walk  gen- 
erally subsides,  while  the  verges  become  higher,  for  which  an 
allowance  must  be  made.  The  same  rule  applies  to  walks 
edged  with  box,  which  are  most  suitable  in  a  kitchen  garden. 

3.  Borders  and  Interior  Compartments.  —  The  width  of  the 
borders  and  size  of  the  compartments  must  be  regulated  by  the 
height  of  the  wall  or  fence,  and  the  extent  of  the  garden.  The 


120  FORMATION    OF    GARDENS. 

best  general  rule  that  can  be  laid  down  is  to  make  the  breadth 
of  the  borders  equal  to  the  height  of  the  wall  or  boundary  fence, 
whatever  it  may  be ;  they  may  be  made  broader,  but  not  nar- 
rower, for  then  they  produce  a  bad  effect;  a  narrow  border 
beside  a  high  fence  is  very  displeasing  to  the  eye. 

The  size  and  number  of  the  compartments  are  determined  by 
the  number  and  disposition  of  the  walks.  It  is  decidedly  a  bad 
plan  to  have  too  many  walks,  as  the  ground  is  not  only  taken 
up  with  them,  which  require  a  deal  of  labor  to  keep  them  clean, 
but  the  effect  of  the  garden  is  lessened.  If  less  than  two  acres 
be  enclosed,  a  walk  running  parallel  with  the  boundary,  say 
twelve  feet  distant  from  it,  and  another  intersecting  the  garden 
in  the  middle,  running  south  and  north,  will  be  sufficient ;  if 
more  than  two  acres  be  enclosed,  another  intersecting  walk,  run- 
ning east  and  west,  may  be  introduced.  If  the  garden  be 
worked  by  horse  labor,  the  larger  the  compartments  the  better ; 
if  wrought  entirely  by  manual  labor,  these  compartments  may 
be  sub-divided  for  the  crops,  by  rows  of  fruit-trees,  or  fruit- 
bushes,  as  may  be  required.  It  should  be  observed,  that  to 
have  a  few  walks,  and  those  of  good  width,  gives  the  garden  a 
better  appearance,  and  is  in  every  way  preferable  to  having  a 
large  number  of  contracted  ones,  and  it  leaves  the  compartments 
to  be  sub-divided  by  alleys  or  other  means,  as  may  be  most  con- 
venient for  access  to  the  crops. 

In  many  gardens,  trellises  or  espalier  rails  are  adopted.  The 
proper  place  for  an  espalier  rail  trellis  is  on  the  inside  of  the 
principal  walks,  leaving  a  border  of  at  least  six  feet.  Many 
gardeners  condemn  them,  arid  perhaps  justly,  in  small  gardens, 
as  it  confines  the  ground  too  much ;  but  in  large  gardens,  espa- 
liers, if  well  managed,  are  both  useful  and  ornamental.  The 
railing  should  be  plain  and  neat,  not  more  than  five  or  six  feet 
high,  with  the  upright  rails,  to  which  the  trees  are  tied,  about 
eight  inches  apart. 

It  is  not  our  purpose,  at  present,  to  dwell  on  the  laying  out 
of  gardens.  We  have  merely  adverted  to  the  subject,  in  so  far 
as  it  is  connected  with  the  object  of  this  treatise. 


FORMATION  OF  GARDENS.  121 

Walls.  —  As  garden  walls  may  be  regarded  as  horticultural 
structures,  we  will  here  make  a  few  remarks  upon  them. 

In  Europe,  walls  are  built  around  gardens  of  all  kinds, 
whether  the  enclosed  space  be  one  or  twenty  acres.  Their 
chief  use  is  for  training  the  more  tender  kinds  of  fruit-trees 
upon  their  southern  aspect.  The  enclosed  space  is  generally 
appropriated  to  the  growth  of  culinary  vegetables,  and  contain- 
ing also  the  hot-houses,  which  occupy  a  part  of  their  south 
aspect.  These  gardens  are  of  various  forms,  and  we  have  seen 
them  circular,  oval,  square,  and  oblong.  The  latter  shape,  with 
the  angular  corners  cut  off,  is  undoubtedly  the  most  desirable 
shape  for  a  vegetable  garden.  The  oval  and  polygonal  forms 
are  preferred  by  some,  on  account  of  their  affording  a  more  equal 
distribution  of  sun  and  shade.  But  we  are  at  a  loss  to  find  out 
how  this  can  be  the  case,  as,  however  a  wall  may  be  placed, 
it  can  only  obtain  a  certain  amount  of  direct  sunshine  during 
the  day,  and  the  inconvenience  resulting  from  the  adoption  of 
these  forms  is  very  considerable,  both  in  the  management  and 
culture  of  the  interior  compartments,  and  in  the  training  of  the 
trees.  Moreover,  an  equal  distribution  of  sunshine  is  not  so 
desirable  as  may  appear ;  as,  while  the  warmest  portion  of  the 
wall  may  be  appropriated  to  the  more  delicate  and  early  fruits, 
the  coldest,  or  northern  portion,  may  be  as  profitably  appropri- 
ated to  late  sorts,  or  for  retarding  earlier  kinds,  both  of  which 
purposes  are  as  useful  as  an  early  aspect. 

In  this  country,  walls  have  been  little  employed  in  the  forma- 
tion of  gardens,  and  only  in  a  few  places  have  they  been 
adopted,  as  at  the  fine  gardens  of  Mr.  Gushing,  at  Watertown, 
and  Col.  Perkins,  at  Brookline,  in  the  vicinity  of  Boston,  —  two 
of  the  finest  gardens  in  this  country.  Some  other  places  have 
also  portions  of  walls  surrounding  the  garden,  but  we  have  seen 
none  where  any  principles  of  design  have  been  adopted  and  car- 
ried out  so  much  as  at  the  former  placet 

*  In  Hovey's  Magazine  of  Horticulture,  pp.  50—53,  vol.  xvi.,  we 
have  described  the  beautiful  gardens  at  this  place,  from  a  visit  which 
we  gave  them  at  that  time.  We  have  subsequently  visited  them,  as 
well  as  many  other  places,  and  still  consider  them  the  finest  gardens  we 
have  seen  in  America.  They  are  made  precisely  in  the  style  of  modern 


122 


FORMATION    OF    GARDENS. 


In  nearly  all  gardens,  trellises  and  wood  fences  are  employed 
instead  of  walls,  as  enclosures  to  the  garden  ground ;  and  these 
are  well  adapted  for  the  purpose,  as  the  fruits  which  require 
the  protection  of  walls  in  England  thrive  and  produce  their 
fruit  in  greater  perfection  as  open  standards  here.  The  utility 
of  walls,  however,  around  a  garden,  cannot  be  doubted,  even  in 
this  country,  especially  as  regards  the  protection  they  afford  to 
trees  trained  on  them,  in  early  spring.  Walls  may  be  consid- 
ered as  useful  to  plants  trained  on  them,  or  near  to  them,  in 
three  ways:  —  first,  by  the  mechanical  shelter  they  afford 
against  cold  winds ;  secondly,  by  giving  out  the  heat  they  had 
acquired  during  the  day;  and,  thirdly,  by  preventing  the  loss  of 
heat  which  the  trees  would  sustain  by  radiation.  [See  Experi- 
ments by  Dr.  Wells,  in  the  third  part  of  this  work,  Section  VI. 
Protection  of  Plant-houses  during  Night.] 

The  same  arguments  which  have  been  applied  in  favor  of 
the  best  aspect  for  hot-houses,  [see  Section  I.,]  are  equally  appli- 
cable to  walls.  In  the  middle  and  southern  states,  we  should 
think  walls  having  a  due  southern  aspect  decidedly  objectiona- 
ble, and,  for  tender  and  delicate  kinds  of  fruit-trees,  would  decid- 
edly prefer  either  a  south-eastern  or  a  south-western  aspect. 

The  height  of  walls,  or  fences  of  any  kind,  round  a  garden, 
should  always  correspond  to  the  space  inclosed.  Twelve  feet 
may  be  taken  as  a  maximum  height.  In  England,  low  walls 

produce  a  greater  effect  in  accelerating  fruit  than  high  ones ; 

i 

English  gardens,  surrounded  with  fine  walls,  with  the  principal  range 
of  hot-houses,  about  300  feet  in  length,  on  the  southern  aspect  of  the 
wall  on  the  north  side  of  the  garden,  and  a  smaller  range  on  the  inside 
of  the  east  and  west  walls,  all  lean-to  houses.  There  are  convenient 
back-sheds  and  other  offices  on  the  north  side  of  the  hot-houses.  There 
is  no  wall  on  the  south  side  of  this  garden,  which  we  think  is  very 
appropriately  dispensed  with.  "We  regard  this  as  a  general  rule,  and 
more  especially  in  gardens  of  small  size,  as  it  gives  the  enclosed  spaces 
a  less  meagre  and  confined  appearance.  This  garden,  alone,  of  any 
which  we  have  seen  in  this  country,  bears  an  impress  of  the  style  and 
genius  cf  Loudon.  And  though  we  have  some  faults  to  find  with  the 
surrounding  grounds,  nevertheless,  we  believe,  taking  it  all  in  all,  it  is 
the  most  perfect  specimen  of  modern  European  gardening  in  this  coun- 
try. 


FORMATION  OF  GARDENS.  123 

but  in  this  country  the  great  radiation  of  heat  from  the  earth, 
during  the  heat  of  summer,  would  render  low  walls  of  little  use. 
On  the  other  hand,  high  walls  have  always  a  gloomy  effect,  and, 
where  it  is  necessary  to  have  high  walls  round  a  garden,  it  is 
better  to  relieve  the  monotony  of  the  wall  by  making  it  of  differ- 
ent heights. 

Hot,  or  flued,  walls  are  very  common  in  European  gardens, 
and  have  been  used  upwards  of  a  century;  and,  in  our  opinion, 
where  walls  can  be  of  any  importance  in  this  country,  in  the 
practice  of  horticulture,  it  must  be  chiefly  as  flued  walls.  In 
summer,  the  protection  of  a  wall  is  not  required  to  ripen  the 
common  fruits,  and  in  hot  summers  they  are  frequently  injuri- 
ous, by  the  attraction  and  radiation  of  heat  during  the  midday 
sun,  by  which  the  leaves  are  sometimes  scorched.  It  must  be 
as  protectors  of  peach  and  apricot  blossoms  in  spring,  and  accel- 
erating the  ripening  of  grapes  in  autumn,  in  which  they  can  be 
most  serviceable  to  the  horticulturist ;  and  for  these  purposes  hot 
walls  are  of  great  benefit.  [See  Wall  Heating,  Part  II.,  Sec.  V.] 

Flued  walls  can  be  built  as  cheap,  if  not  cheaper,  than  solid 
ones,  and  are  invariably  built  of  brick;  indeed,  a  considerable 
saving  of  material  is  effected,  as  little  more  than  half  of  the 
bricks  required  to  build  a  solid  wall  will  build  a  hollow  or  flued 
wall ;  and,  unless  a  flued  wall  be  desired,  it  is  better  to  dispense 
with  a  wall  altogether,  for  although  a  wooden  paling  will  not  ab- 
sorb so  much  heat  as  a  brick  wall,  as  a  structure  for  mechanical 
shelter  it  is  in  every  way  equal  to  it,  providing  it  be  boarded 
perfectly  close,  and  sufficiently  high.  The  comparative  cheap- 
ness of  wooden  fences,  for  gardens,  must  give  them  the  prefer- 
ence, and  the  comparative  beauty  of  brick  walls  and  wood 
palings  is  a  matter  of  taste  which  must  be  decided  by  the  pro- 
prietor. 

Walls,  or  close  palings,  must,  in  all  cases,  be  faced  with  a 
light  trellis,  made  of  laths  or  wire,  to  which  the  trees  can  be 
trained.  The  injury  resulting  to  trees  nailed  on  walls,  in  our 
gardens,  is  owing  to  their  touching  the  material  of  the  wall. 
The  branches  should  be  trained  at  least  six  or  eight  inches  from 
the  surface,  so  as  to  admit  a  stratum  of  air  between  the  wall 


124  FORMATION  OF  GARDENS. 

and  the  branches.  When  this  is  attended  to,  no  injury  results 
to  the  foliage,  even  in  the  hottest  of  seasons. 

Boarded  walls  have  long  been  used  in  northern  countries,  and 
are  frequently  made  to  incline  considerably  towards  the  north, 
so  as  to  present  a  better  angle  to  the  sun's  rays  than  if  standing 
upright ;  an  expedient  which  here  is  unnecessary. 

We  cannot  help  thinking  that  flued  walls  are  worthy  of  more 
attention  from  horticulturists  than  they  seem  to  have  had,  espe- 
cially when  early  fruit  is  desired,  without  the  trouble  and  expense 
of  a  glazed  structure,  as  an  expedient  for  a  hot-house.  [See  cut 
50,  in  the  next  part  of  this  work,  page  245.] 


PART  II.    HEATING. 

SECTION    I/ 

PRINCIPLES  OF  COMBUSTION. 

1.  To  warm  hot-houses,  etc.,  most  economically  and  efficiently, 
we  must  study  not  only  the  principles  of  heating,  but,  also, 
the  principles  of  combustion.  And  as  we  are  yet  far  from, 
having  obtained  a  complete  knowledge  of  the  most  profitable 
manner  of  submitting  coal  and  other  kinds  of  fuel  to  the  process 
of  combustion,  or,  of  applying  the  caloric  so  obtained  to  increase 
the  temperature  of  hot-houses,  it  will,  therefore,  be  desirable  to 
begin  at  the  beginning  of  this  part  of  our  work,  and  before  treat- 
ing on  the  different  mechanical  contrivances  in  common  use  for 
the  generation  and  diffusion  of  heat  by  combustion,  let  us  first 
consider  the  principles  upon  which  these  ends  are  to  be  obtained. 

The  subject  before  us  involves  a  consideration  of  the  nature 
and  properties  of  the  various  kinds  of  fuel.  It  examines  the 
chemical  action  of  their  several  constituents  on  each  other.  It 
applies  those  inquiries  to  the  class  of  chemical  results  which 
may  be  useful,  and  avoids  those  which  are  injurious.  It  involves 
also,  in  an  especial  degree,  the  closest  observation  on  the  sepa- 
rate influences  which  each  of  the  constituents  of  atmospheric 
air  exercises  on  combustible  bodies,  in  the  generation  of  those 
extraordinary  elements  of  nature,  heat  and  light.  And,  finally, 
it  investigates  the  cause  and  character  of  flame  and  smoke,  and 
the  influence  these  have  on  the  former. 

Economy  of  fuel  being  one  of  the  most  important  points  to  be 
sought  for  in  a  heating  apparatus,  we  must  inquire  whether  our 
common  furnaces  be  so  constructed  as  to  give  us  the  maximum 
quantity  of  caloric,  for  the  fuel  that  is  consumed.  We,  there- 


126  HEATING. 

fore,  must  look  into  the  furnace,  and  consider  chemically  as  well 
as  practically,  the  operations  which  are  there  going  on,  so  that 
we  may  improve  its  arrangements,  and  adapt  them  so  as  to  give 
full  practical  effect  to  the  several  processes  which  constitute 
combustion. 

To  enable  our  practical  readers  to  obtain  a  more  accurate 
knowledge  of  the  processes  going  on  in  the  furnace,  and  of  the 
results  of  the  common  mode  of  managing  the  fires  of  extensive 
forcing  houses,  we  will  enter  more  fully  upon  the  constituents 
of  coal,  and  the  gases  thereby  generated,  which  form  such  an 
important  part  of  the  fuel  itself,  and  which,  by  their  escape  into 
the  atmosphere  from  the  chimney,  or  into  the  atmosphere  of  the 
house  from  the  flue,  become  the  source  of  immense  loss  of  heat. 
And,  in  the  latter  case,  the  loss  is  more  than  doubled,  as  they 
are  destructive  in  the  highest  degree  to  every  kind  of  vegetable 
life. 

In  undertaking  to  show  how  these  evils  may  be  remedied,  we 
must  not  be  understood  to  concur  in  the  exploded  opinion,  that 
these  gases  may  be  consumed  by  the  methods  hitherto  used  for 
that  purpose,  viz.,  by  passing  the  smoke  over  a  body  of  red-hot 
fuel  at  a  distance  from  the  burning  and  smoking  mass.  And 
however  desirable  it  may  be  to  know  of  some  way  of  preventing 
smoke  from  being  emitted  in  clouds  from  the  chimney  of  hot- 
houses, yet,  if  we  can  discover  no  other  method  of  obviating  the 
evil,  except  "  burning  it,"  according  to  the  common  acceptation 
of  that  word,  I  fear  we  must  continue  to  put  up  with  the  loss 
and  annoyance  as  it  is. 

It  is  not  our  purpose  here  to  show  how  the  smoke  from  fuel 
may  be  burned ;  but  rather,  we  will  attempt  to  show  how  fuel 
may  be  burned  without  smoke.  And,  let  it  be  observed,  this 
distinction  involves  the  main  question  of  economy  of  fuel. 

When  smoke  is  once  produced  in  a  furnace  or  flue,  we  believe 
it  to  be  as  difficult  to  burn  it,  (and  convert  it  to  heating  pur- 
poses,) as  to  burn  and  convert  the  smoke  issuing  from  the  flame 
of  a  candle  to  the  purposes  of  light.  If,  indeed,  we  could  collect 
the  smoke  and  unconsumed  gases  of  a  furnace,  and  separate 
them  from  the  products  of  combustion  which  the  flues  carry  off, 
they  might,  subsequently,  be  made  instrumental  to  the  purposes 


PRINCIPLES    OF    COMBUSTION.  127 

of  heat ;  but,  by  the  common  method  of  constructing  furnaces, 
their  collection  is  impossible. 

When  we  see  smoke  issuing  from  the  flame  of  an  ill-adjusted 
common  lamp,  the  heat  and  light  are  diminished  in  quantity.  Do 
we  attempt  to  burn  that  smoke  ?  No ;  it  would  be  impossible. 
Again,  when  we  see  a  well-adjusted  lamp  burn  without  pro- 
ducing any  smoke,  the  flame  is  clear  and  white.  But  here,  the 
lamp  has  not  burned  its  smoke ;  it  has  burned  without  smoke; 
and  it  remains  to  be  shown  why  the  same  methods  may  not  be 
employed  with  regard  to  common  furnaces,  whereby  they  may 
burn  without  smoke,  and  thereby  give  out  a  greater  quantity  of 
heat,  as  in  the  case  of  the  common  and  Argand  lamp,  since  the 
elements  of  combustion  in  both  cases  are  the  same. 

2.  In  pointing  out  the  leading  characteristics  in  the  use  of 
coals,  it  is  unnecessary  to  enter  into  detail  of  the  various  pro- 
cesses of  gasefaction.  We  will,  however,  give  this  part  of  our 
subject  a  little  attention,  as  the  greater  portion  of  the  practicable 
economy  in  the  use  of  coal,  and  the  management  of  furnaces, 
will  be  found  more  or  less  connected  with  the  combustion  of  the 
gases  which  arise  from  the  combustion  of  fuel,  and  as  the  numer- 
ous combinations  of  which  they  are  susceptible  embrace  the 
whole  range  of  temperature,  from  that  of  flame  down  to  the 
refrigeratory  point. 

The  subject  of  gaseous  combinations,  then,  is  undoubtedly  an 
important  part  of  our  inquiry.  And  those  who  would  study  the 
economy  of  fuel,  and  the  obtaining  from  it  the  greatest  quantity 
of  heat,  cannot  altogether  dispense  with  the  part  of  our  subject 
which  at  present  lies  before  us.  Though  it  may  not  appear 
equally  interesting  and  important  to  every  one,  it  is,  neverthe- 
less, the  alpha  and  omega  of  the  whole  process  of  combustion. 
The  gardener  may  say,  what  has  this  to  do  with  gardening  ? 
But  we  tell  him,  plainly,  that  this  is  an  essential  part  of  his 
business,  which  will  be  generally  admitted  by  intelligent  men, 
that  so  long  as  a  furnace  is  connected  with  a  hot-house,  and 
fuel  consumed  in  that  furnace,  this  must  necessarily  be  a  part 
of  his  business. 

On  the  application  of  heat  to  bituminous  coal,  the  first  result 


128  HEATING. 

is  its  absorption  by  the  coal,  and  the  consequent  disengagement 
of  gas,  from  which  all  that  subsequently  bears  the  character  of 
flame  is  exclusively  derivable.  This  gas,  whether  it  be  in  a 
close  retort,  or  in  a  furnace,  is  associated  with  several  other 
substances,  more  or  less  tending  to  deteriorate  its  inflammable 
properties  and  powers  of  giving  out  heat  and  light.  In  the 
preparation  of  gas,  or  smoke,  for  illuminating  purposes,  these 
impurities  are  separated,  and  the  pure  gas  alone  is  used.  As, 
however,  this  separation  cannot  be  effected  in  a  common  furnace, 
arid,  as  the  entire  gaseous  products  of  the  coal,  good  and 
bad,  are  indiscriminately  consumed  together  as  they  are  gener- 
ated, it  is  the  more  incumbent  on  us  to  be  cautious,  lest,  by  any 
injudicious  arrangement,  we  force  these  impurities  into  more 
active  energy,  and  thus  increase  their  deleterious  power. 

We  will  not  stop  here  to  consider  the  nature  of  those  impuri- 
ties arising  out  of  the  unions  of  sulphur,  and  the  other  injurious 
constituents  of  coal,  although  they  exercise  a  mischievous  in- 
fluence on  the  calorific  effect  of  the  gas  burning  in  the  furnace, 
but  will  consider  those  constituents  alone,  which  unite  in  form- 
ing the  useful  gases,  and  from  which  we  are  to  derive  heat. 

These  constituents  are  the  hydrogen  and  the  carbon.  And 
the  unions  which  alone  concern  us  here,  are,  first,  carburetted 
hydrogen;  and,  second,  bi-carburetted  hydrogen,  commonly 
called  olefiant  gas.  These  two,  and  their  unions  with  the  air, 
in  the  process  of  combustion,  we  will  shortly  examine. 

Gases,  as  well  as  other  bodies,  endowed  with  the  power  of 
giving  out  heat  and  light,  have  been  called  combustible.  This 
term  has  been  a  source  of  much  error  in  practice,  from  a  mis- 
conception of  its  meaning,  under  the  received  impression  that 
combustibles  possess,  in  some  undefined  manner,  and  within 
themselves,  the  faculty  of  burning.  And,  though  every  person 
knows  that  they  will  not  burn  without  air,  still  the  part  which 
air  acts  in  the  process  is  but  little  inquired  into.  It  is  but  lately 
that  the  nature  of  this  union  of  the  gas  with  the  air  has  come  to 
be  fully  understood ;  and,  although  the  abstract  question  as  re- 
gards the  immediate  cause  of  that  chemical  action,  which  we 
,?all  combustion,  may  continue  to  be  disputed,  and  new  theories 
continue  to  be  broached,  still,  for  all  practical  purposes,  it  is 
sufficiently  defined  and  understood. 


PRINCIPLES    OF    COMBUSTION.  129 

And  here  we  are  called  on  to  inquire,  wiih  reference  to  the 
gases  under  consideration,  whether  there  are  any  peculiar 
conditions  which  can  influence  the  amount  of  heat  to  be  ob- 
tained from  them  ?  and,  if  so,  what  they  are  ?  This,  again, 
involves  other  questions  in  reference  to  air,  and  the  part  which 
it  has  to  act  in  the  process ;  and  thus  we  find  ourselves  intro- 
duced into  the  chemistry  of  combustion. 

One  advantage  of  receiving  the  subject  in  this  light,  is,  that 
we  shall  see  how  idle  would  be  any  calculations  or  arrangements 
as  to  the  dimensions  or  details  of  a  furnace,  before  we  had  well 
examined  and  understood  the  rationale  of  that  process  on  which 
these  details  must  necessarily  be  contingent.  For  what  chemist 
would  begin  by  deciding  on  the  dimensions  of  his  retort,  or  other 
apparatus,  before  he  had  considered  the  particular  purposes  to 
which  they  were  to  be  applied  ?  Yet  such  is  the  every-day 
practice  of  those  who  profess  to  instruct  us  in  these  matters. 
The  absurdity  of  this  practice,  and  the  dangers  into  which  it 
leads  practical  men,  will  be  more  apparent  when  we  come  to 
consider  the  nature  of  heating  apparatuses,  and  the  powers  and 
properties  which  belong  to  each. 

Combustibility,  then,  is  not  a  quality  of  the  combustible  taken 
by  itself.  It  is  merely  a  faculty  which  may  be  brought  into 
action  through  the  instrumentality  of  a  corresponding  faculty  in 
some  other  body.  It  is,  in  the  case  now  before  us,  the  union  of 
the  combustible  with  oxygen,  and  which,  for  this  reason,  is 
called  the  supporter.  Neither  of  which,  however,  when  taken 
alone,  can  be  consumed. 

To  effect  combustion,  then,  we  must  have  a  combustible,  and 
a  supporter  of  combustion.  Strictly  speaking,  combustion 
means  union;  but  it  means  chemical  union,  —  one  of  the  ac- 
companying incidents  of  this  union  being  the  emission  of  heat 
and  light.  What  the  nature  of  heat  is,  or  how  it  is  liberated 
during  chemical  action,  it  is  not  our  province  to  consider; 
nor  does  it  relate  much  to  our  present  inquiry.  Sufficient  for  our 
present  purpose,  is  the  fact,  that  the  chemical  union  of  the  com- 
bustible, (the  coal,)  and  the  supporter  of  combustion,  (the  oxygen 
of  the  air,)  is  the  cause  of  heat  being  given  off;  and,  further, 


130  HEATING. 

that  exactly  in  the  ratio  that  such  union  is  complete,  is  the  quan- 
tity of  heat  increased. 

But  we  have  not  the  means  of  obtaining  this  necessary  sup- 
porter in  sufficient  quantity,  in  a  separate  state,  except  at  an  ex- 
pense which  would  render  it  incompatible  with  the  purposes  of 
a  furnace.  Our  only  alternative  then  is  to  apply  to  the  atmos- 
phere, of  which  it  forms  a  part,  in  order  to  satisfy  our  wants. 
Had  we  to  purchase  this  oxygen,  we  would,  necessarily,  be  more 
economical  of  its  use,  and  inquire  more  respecting  its  application. 
But,  finding  an  abundant  supply  at  hand,  in  the  atmosphere, 
and  obtaining  it  without  expense,  we  are  careless  of  its  use,  and 
unconscious  of  its  value,  and  take  no  note  of  the  large 
quantity  of  the  noxious  ingredients  with  which  it  is  accompanied, 
or  loss  sustained,  by  diminishing  the  supply;  and  hence,  many 
of  the  evils,  such  as  bad  apparatus,  bad  fuel,  and  bad  furnaces, 
might  be  easily  remedied,  were  the  properties  of  these  gases  fully 
understood. 

The  unions  we  have  now  to  consider  are  those  which  take 
place  between  the  constituents  of  the  coal  and  the  atmospheric 
air,  namely,  the  hydrogen  and  carbon  of  the  former,  and  the 
oxygen  of  the  latter.  Dr.  Ure  calls  the  carbonaceous  part  of 
coal,  "  the  main  heat-giving  constituent."  In  this  he  must  be 
understood  to  include  that  portion  of  the  carbon  which  forms 
one  of  the  constituents  of  the  gases  alluded  to,  and,  although, 
for  the  purposes  of  the  furnace,  so  much  value  is  set  upon  the 
solid  part — the  coke  —  we  must  not,  on  that  account,  undervalue 
the  heat-giving  properties  of  the  gas.  Indeed,  the  extent  of 
those  powers  is  strikingly  brought  before  us,  by  the  fact,  that  for 
every  ton  of  bituminous  coal  no  less  than  10,000  cubic  feet  of 
gas  are  obtained. 

When  we  consider  the  immense  heating  powers  of  such  a 
mass  of  flame  as  would  be  produced  by  10,000  feet  of  gas,  we 
cannot  resist  the  conclusion,  that  there  must  be  something  es- 
sentially wrong  in  the  mode  of  bringing  it  into  action  within  a 
furnace,  as  compared  to  its  well  known  efficacy  in  an  argand 
burner.  That  this  is  the  fact,  will  appear  manifest  as  we  pro- 
ceed. And  one  of  our  objects  is  to  show  how  greater  heat  may 
be  obtained  by  the  combustion  of  the  volatile  products  of  the 


PRINCIPLES   OF   COMBUSTION.  131 

coal,  than  by  allowing  the  whole  body  of  gas  to  escape  into  the 
atmosphere. 

Let  us  bear  in  mind,  that  smoke  is  always  the  same,  whether 
it  may  be  generated  in  a  common  fire-place,  in  a  furnace,  or  in  a 
retort;  and  that,  strictly  speaking,  it  is  not  inflammable,  as  by 
itself  it  can  neither  produce  flame  nor  permit  the  continuance 
of  flame  in  other  bodies,  as  is  proved  from  the  fact  that  a  lighted 
taper  being  introduced  into  a  jar  of  coal  gas,  (or  smoke,)  is 
instantly  extinguished. 

How,  then,  is  it  to  be  consumed  or  prevented,  and  rendered 
available  for  the  production  of  heat  ?  The  answer  is,  solely  by 
effecting  a  chemical  union,  not  with  the  air  merely,  as  is  the 
dangerous  notion,  but  with  the  oxygen  of  the  air,  —  the  "sup- 
porter" of  flame,  the  heat-giving  constituent  of  the  air,  in  given 
quantities,  and  at  a  given  temperature. 

This  at  once  opens  the  main  question,  What  are  these  quan- 
tities, and  what  is  this  temperature  ?  and,  are  there  any  other 
conditions  requisite  for  effecting  the  chemical  union  of  the 
oxygen  of  the  air  with  the  inflammable  gas,  to  the  best 
advantage  ? 

Effective  combustion,  for  practical  purposes,  is,  in  truth,  a 
question  more  as  regards  the  air  and  the  gas  ;  and  the  former, 
as  referable  to  our  object,  would  appear  better  entitled  to  the 
term  combustible  than  the  latter,  inasmuch  as  the  heat  is  in- 
creased in  proportion  to  the  quantity  of  air  we  are  enabled  to 
use  advantageously.  Besides  that,  we  have  no  control  over  the 
gas  after  having  thrown  the  fuel  on  the  furnace,  but  we  can 
exercise  a  control  over  the  air,  as  we  shall  show,  in  all  the 
essentials  of  perfect  combustion.  It  is  this  which  has  done  so 
much  for  the  perfection  of  the  lamp,  and  may  be  rendered 
equally  available  for  the  furnace. 

Now,  although  this  control,  and  the  management  arising  out 
of  it,  influences  the  question  of  perfect  or  imperfect  combustion, 
and,  therefore,  affects  that  of  economy,  yet,  strange  to-  say,  in  an 
age  when  chemical  science  is  so  advanced,  and  in  a  matter  so 
purely  chemical,  this  is  precisely  what  is  attended  to  in  practice. 
The  how,  the  when,  and  the  where,  this  controlling  influence 
over  the  admission  and  the  action  of  the  air  is  to  be  exercised, 
12 


132  HEATING. 

are  points  demanding  the  most  attentive  consideration  from  all 
who  are  interested  in  these  matters. 

Much  confusion  at  present  prevails  in  all  that  regards  hot- 
house furnaces,  as  well  in  their  practical  working  as  regards  the 
admission  of  air  and  the  combustion  of  fuel.  In  commenting 
briefly  upon  the  constituents  of  coal  smoke,  or  coal  gas,  car- 
buretted  hydrogen,  and  the  quantity  of  air  required  for  their 
combustion,  we  will  be  as  explicit  as  possible,  without  going 
more  into  scientific  detail  than  is  consistent  with  the  means  and 
opportunities  of  that  class  of  practical  men  for  whom  we  write. 

3.  The  first  step  towards  effecting  the  perfect  combustion  of  any 
combustible  gas,  is  the  ascertaining  the  quantity  of  oxygen  with 
which  it  will  chemically  combine,  and  the  quantity  of  air  re- 
quired for  supplying  such  quantity  of  oxygen.  Here,  then,  we 
are  called  on  for  strict  chemical  proofs  —  these  several  quantities 
depending,  not  on  the  dictum  of  any  chemist,  but  on  the  faculty 
which  each  particular  gas  possesses  of  combining  with  certain 
definite  proportions  of  the  other  —  the  supporter  ;  these  respec- 
tive proportions  being  termed  "  equivalents"  or  combining  vol- 
umes. This  doctrine  of  equivalents  must,  therefore,  be  under- 
stood before  we  can  be  prepared  to  admit  the  necessity  of  any 
precise  quantities.  This  question,  as  to  quantity,  is  also  the 
more  important  when  we  consider  that  the  quantity  of  effective 
heat  obtained  by  the  combustion  of  any  body,  will  be  in  exact 
relation  to  the  quantity  of  oxygen  with  which  it  will  chemically 
combine. 

Let  us  begin,  then,  by  inquiring  into  the  constitution  of  the 
coal  gas,  and  the  relative  proportions  in  which  its  constituent 
elements  are  combined,  as  these  necessarily  govern  the  propor- 
tions in  which  it  will  combine  with  the  oxygen  of  the  air. 

Now,  the  doctrine  of  "  equivalents,"  that  all-convincing  proof 
of  the  truths  of  chemistry,  being  clearly  defined  and  understood, 
reduces,  to  a  mere  matter  of  calculation,  that  which  would 
otherwise  be  a  complicated  tissue  of  uncertainties.  And  let  no 
mechanic  feel  alarmed  at  this  introduction  to  "  elementary  atoms  " 
and  "  chemical  equivalents,"  or  imagine  it  will  demand  a  deeper 
knowledge  of  chemistry  than  is  compatible  with  his  sources  of 


PRINCIPLES    OF    COMBUSTION.  133 

information;  neither  let  him  suppose  he  can  dispense  with  the 
knowledge  of  this  branch  of  the  subject*  if  he  has  anything  to 
do  with  the  combustion  of  coal.  Without  it,  he  is  at  the  mercy 
of  every  speculative  "smoke-burning"  pretender;  whereas, 
with  it,  his  mind  will  be  at  once  opened  to  the  simplicity  and 
efficiency  —  I  may^  add,  to  the  truth  and  beauty,  of  nature's 
processes,  as  regard  combustion. 

There  is  not,  indeed,  a  more  curious  or  instructive  part  of  the 
inquiry  than  that  respecting  the  conditions  and  proportions  in 
which  the  compound  gases  enter  into  union  with  the  constituents 
of  the  air;  neither  is  there  one  more  intimately  connected  with 
the  practical  details  of  our  furnaces.  These  introductory  remarks 
are,  therefore,  necessary  for  those  who  are  not  already  familiar 
with  it.  Indeed,  without  some  information  on  this  head,  the 
unions  of  the  gases  might  appear  capricious  or  uncertain; 
whereas,  in  fact,  they  are  regulated  by  the  most  exact  laws,  and 
subject  to  the  most  unerring  calculations/* 

*  Mr.  Parkes  observes  :  —  "  We  are  unfurnished  with  any  definite, 
determinate  experiments  regarding  the  proportions  in  which  air  and  fuel 
unite  during  combustion.  We  are,  practically  speaking,  altogether  ig- 
norant of  the  mutual  relations  which  subsist  between  the  combustible  and 
the  supporter  of  combustion^  (the  fuel  and  the  oxygen  ;)  and,  though  we 
know  that,  without  oxygen,  we  cannot  elicit  heat  from  coal,  we  have  yet 
to  discover  the  most  productive  combinations  of  the  two  elements. 

"  Here,  then,  remains  a  wide  field  for  research  and  experiment,  wor- 
thy, and,  indeed,  requiring  the  labors  of  a  profound  chemist." 

These  matters  are  now  better  understood,  and  those  "most  productive 
combinations  "  rendered  familiar  and  certain,  by  the  labors  of  that  "  pro- 
found chemist,"  John  Dalton,  who  first  drew  the  attention  of  the  chemical 
world  to  the  subject  of  equivalent  proportions,  and  taught  us  the  impor- 
tance and  necessity  of  ascertaining  those  proportions  —  in  fact,  of 
"  reasoning  by  the  aid  of  the  balance." 

Dalton's  papers  were  first  read  before  the  Manchester  Philosophical 
Society,  and  published  in  their  memoirs,  in  the  year  1803.  These  vol- 
umes are  very  scarce,  and  I  have  not  been  able,  anywhere,  to  meet  with 
a  complete  copy  of  them.  The  Royal  Institution,  where  Davy  brought 
his  great  discoveries  to  light,  contains  but  the  five  volumes  of  the  first 
series.  These  volumes,  or,  at  least,  the  papers  of  Dalton,  should  be  re- 
published,  for  the  purpose  of  showing  the  correct  chain  of  reasoning 
by  which  the  mind  of  that  acute  philosopher  proceeded. 


134  HEATING. 

Much  of  the  apparent  complexity  which  exists  on  this  head 
arises  from  the  disproportion  between  the  relative  volumes,  or 
folk,  of  the  constituent  atoms  of  the  several  gases,  as  compared 
with  their  respective  weights. 

For  instance,  an  atom  of  hydrogen  (meaning  the  smallest 
ultimate  division  into  which  it  is  supposed  to  be  resolvable)  is 
double  the  bulk  of  an  atom  of  carbon  vapor  ;  yet  the  latter  is 
$ix  times  the  weight  of  the  former. 

Again,  an  atom  of  hydrogen  is  double  the  bulk  of  an  atom  of 
oxygen ;  yet  the  latter  is  eight  times  the  weight  of  the  former. 

So  of  the  constituents  of  atmospheric  air,  nitrogen  and 
oxygen.  An  atom  of  the  former  is  double  the  bulk  of  an  atom 
of  the  latter ;  yet,  in  weight,  it  is  as  fourteen  to  eight. 

A  further  source  of  apparent  complexity  arises  from  the 
faculty  of  condensation,  or  diminution  of  bulk,  which,  in  certain 
cases,  attends  the  union  of  the  gases.  For  example,  one  volume 
of  oxygen  and  two  volumes  of  hydrogen,  when  united,  condense 
into  a  volume  equal  to  that  of  the  hydrogen  alone,  (the  weight 
being,  of  course,  the  sum  of  both ;)  that  is  to  say,  one  cubic 
foot  of  oxygen  chemically  combined  with  two  cubic  feet  of 
hydrogen  condense  into  the  bulk  of  two  cubic  feet :  and  so  on, 
each  union  bearing  its  now  ratio  of  volume  and  weight.  This 
apparent  complexity,  however,  we  shall  soon  see  give  way  to  a 
systematic  consideration  of  the  subject. 

We  have  stated  that  there  are  two  descriptions  of  hydro-carbon 
gases,  in  the  combustion  of  which  we  are  concerned ;  both  being 
generated  in  the  furnace,  and  even  at  the  same  time,  namely, 
the  carburetted  and  bi-carluretted  hydrogen  gases.  For  the 
sake  of  simplifying  the  explanation,  I  will  confine  myself  to  the 
first,  as  forming  the  largest  proportion  of  the  gas  to  be  consumed, 
namely,  the  carburetted  hydrogen,  or  common  coal  gas,  as  I  shall 
call  it  for  the  sake  of  brevity. 

Now  as,  during  combustion,  the  atoms  of  this  gas  become 
decomposed,  and  its  constituents  separated  ;  and  as  these  will 
be  found  to  exercise  separate  influences  during  the  process,  it  is 
essential  that  we  examine  them  as  to  their  respective  properties, 
weights,  and  volumes. 

On  analyzing  this  mixed  gas  we  find  it  to  consist  of  two  vol- 


PRINCIPLES    OF    COMBUSTION. 


135 


umes  of  hydrogen  and  one  of  carbon  vapor;  the  gross  bulk 
of  these  three  being  condensed  into  the  bulk  of  a  single  atom  of 
hydrogen  ;  that  is,  into  two  fifths  of  their  previous  bulk,  as  shown 
in  the  annexed  figures.  Let  figure  A  represent  an  atom  of  coal 
gas  —  carburetted  hydrogen  —  with  its  constituents,  carbon  and 
hydrogen ;  the  space  enclosed  by  the  lines  representing  the  rela- 
tive size  or  volume  of  each ;  and  the  numbers  representing  their 
respective  weights  —  hydrogen  being  taken  as  unity  both  for  vol- 
ume and  weight/* 

Carburetted  Hydrogen.          Bi-carburetted  Hydrogen. 


A. 


its 

constituents. 


1  atom  of 
Hydrogen, 
weight  1. 


1  atom  of 
Hydrogen, 
weight  1. 


1  atom  of 
Carbon,  6. 


its 

constituents, 


1  atom  of 
Hydrogen, 
weight  I. 


1  atom  of 
Hydrogen, 
weight  1. 


1  atom  of 
Carbon,  6. 


1  atom  of 
Carbon,  6. 


*  "  Ce  gaz  (carburetted  hydrogen)  est  compose  de  75.17  parties  (by 
weight)  de  carbone,  et  24.33  d'hydrogene;  ou,  d'un  volume  de  carbone 
gazeux  et  quatre  volumes  de  gaz  hydrogene,  condenses  a  la  moitie  due 
volume  de  ce  dernier,  ou,  aux  2/5  du  volume  total  du  gaz,  de  maniere 
que  de  cinq  volumes  simples,  il  n'en  resulte  pas  rflus  de  deux  de  la  com- 
binaison."—  Berzelius,  vol.  i.,  p.  330. 


136 


HEATING. 


Or  they  may  be  represented  thus : 
Carburetted  Hydrogen. 


The  above 

Gas,          I  its  constituents, 


Bi-carburetted  Hydrogen. 


its  constituents, 


Although  not  intending  to  take  any  further  notice,  in  this 
place,  of  the  bi-carburetted  hydrogen,  I  have,  however,  annexed 
the  above  diagrams,  representing  this  gas  and  its  constituents, 
that  both  may  be  under  view  at  the  same  time  ;  and  by  which  it 
will  be  seen,  that  although,  in  volume,  the  two  gases  are  precisely 
the  same,  there  is  yet  double  the  quantity  of  carbon  in  the  bi-car- 
buretted  that  there  is  in  the  carburetted  hydrogen :  this  circum- 
stance is  of  great  importance,  and  must  be  kept  in  our  recollec- 
tion, as  these  proportions  will  be  found  to  have  a  considerable 
influence  during  the  subsequent  process  of  its  combustion.  ^ 

*  The  mode  of  representing  the  volumes  of  gas,  by  rectangular  figures, 
as  adopted  by  Mr.  Brande  and  other  chemists,  is  favorable,  so  far  as 
tingle  atoms  are  concerned,  inasmuch  as  the  eye  at  once  recognizes  the 


PRINCIPLES    OF    COMBUSTION. 


137 


I  would  here  observe  on  the  importance  of  keeping  in  mind 
this  double  relation  of  weight  and  volume,  and  the  atomic  consti- 
tution of  these  gases,  as  it  will  prevent  much  of  that  confusion 
which  too  often  embarrasses  those  who  are  not  familiar  with 
the  subject  of  gaseous  combinations. 

Let  us  now,  in  the  same  analytical  manner,  examine  an  atom 
of  atmospheric  air,  the  other  ingredient  in  combustion. 

Atmospheric  air  is  composed  of  two  atoms  of  nitrogen  and  one 
atom  of  oxygen :  and  here  again  we  find  a  great  disproportion 
between  the  relative  volumes  of  these  constituents ;  one  atom  of 
nitrogen  being  double  the  volume  of  an  atom  of  oxygen,  while 
their  relative  weights  are  as  14  to  8 :  the  gross  volume  of  the 
nitrogen,  in  air,  being  thus  four  times  that  of  the 'oxygen;  and 
in  weight^  as  28  to  8,  as  shown  in  the  annexed  figure. 

Atmospheric  Air,      (or  thus,)         Atmospheric  Air. 


r 

1  atom  of 

Nitrogen, 

Jl 

weight  14. 

8 

1  atom  of 
Nitrogen, 

equal 
to 

II 

51 

weight  14. 

o 

1  atom  of 

i 

Oxygen,  8. 

Here  we  are  relieved  from  the  complexity  arising  out  of  any 
difference  in  volume  between  these  constituents,  when  united  and 
when  separate.  In  the  coal  gas  we  found  the  constituents  con- 
densed into  two  fifths  of  their  gross  bulk  when  separate :  this, 
we  see,  is  not  the  case  with  air  ;  an  atom  of  which  is  the  same, 
both  as  to  bulk  and  weight,  as  the  sum  of  its  constituents. 

relation  between  volumes  and  half  volumes.  As,  however,  I  shall  have  to 
do  with  masses  of  these  gases,  I  have  adopted  circular  figures,  the  rela- 
tion between  the  sizes  of  the  volumes  of  the  different  gases  being  the 
same. 


138  HEATING. 

Thus,  we  find,  the  oxygen  —  the  heat-giving  constituent  of 
the  air  —  bears  a  proportion  in  volume  to  that  of  the  nitrogen,  as 
1  to  5 ;  there  being,  in  fact,  but  20  per  cent,  of  oxygen  in  atmos- 
pheric air,  and  no  less  than  80  per  cent,  of  nitrogen ;  a  circum- 
stance which  should  never  be  lost  sight  of  in  all  that  has  to  do 
with  its  admission  and  application. 

Having  shown  the  composition  of  coal  gas,  and  also  of  air, 
with  the  weights  and  volumes  of  their  respective  constituents, 
we  now  proceed  to  the  ascertaining  the  separate  quantity  of  oxy- 
gen required  by  each  of  those  constituents,  so  as  to  effect  its  per- 
fect combustion,  and  produce  the  largest  quantity  of  available 
heat ;  in  other  words,  to  find  the  "  chemical  equivalent"  or  vol- 
ume of  air,  required  for  the  saturation  of  this  mixed  gas. 

Now,  this  is  to  be  decided,  not  by  the  quantity  of  air  we  may 
admit  or  force  into  the  furnace,  but  solely  by  the  faculty  with 
which  each  of  these  constituents  is  endowed  of  uniting  chemically 
with  the  oxygen. 

With  respect  to  this  power,  or  faculty  of  reciprocal  saturation, 
the  first  great  natural  law  is,  that  bodies  combine  in  certain  fixed 
proportions  only,  —  a  remarkable  feature  in  this  law,  as  far  as 
gaseous  bodies  are  concerned,  being,  that  it  has  reference  both  to 
volume  and  weight ;  thus,  by  their  concurrence,  establishing  the 
principle  which  now  no  longer  admits  of  any  doubt.  * 

The  important  bearings  of  this  great  elementary  principle  of 
proportionate  combination  cannot  be  more  strikingly  illustrated, 
or  its  influence  rendered  more  familiar,  than  in  the  several  com- 

*  "  L'experience  a  demontre  que,  de  meme  que  les  elemens  se  com- 
.binent  dans  des  proportions  fixes  et  multiples,  relativeraent  a  leur  poids, 
fls  se  combinent  aussi,  d'une  maniere  analogue,  relativement  a  leur 
volume,  lorsqu'ils  sont  a  1'etat  de  gaz :  en  sorte  qu'un  volume  d'un 
element  se  combine,  ou,  avec  un  volume  egal  au  sien,  ou  avec  2,  3,  4  et 
plus  de  fois  son  volume  d'un  autre  element  a  1'etat  de  gaz.  En  com- 
parant  ensemble  les  phenomenes  connus  des  combinaisons  de  substances 
gazeuses,  nous  decouvrons  les  memes  lois  des  proportions  fixes,  que  celles 
que  vous  venons  de  deduire  de  leurs  proportions  en  poids  :  ce  qui  donne 
lieu  a  une  maniere  de  se  representer  les  corps,  qui  doivent  se  combiner, 
sous  des  volumes  relatifs  a  1'etat  de  gaz.  Les  degres  de  combinaisons 
sont  absolument  les  memes,  et  ce  qui  dans  1'une  est  nomme  atome,  est 
dans  Vautre  apelle  volume}1  —  Berzelius,  vol.  iv.,  p.  549. 


PRINCIPLES   OF   COMBUSTION. 


139 


binations  of  which  the  elements  of  atmospheric  air  are  suscepti- 
ble, and  the  extraordinary  changes  of  character  and  properties 
which  accompany  the  changes,  in  the  relative  quantities  alone, 
of  the  combining  elements. 

FQT  instance,  oxygen  unites  chemically  with  nitrogen  in  five 
different  proportions,  forming  five  distinct  bodies,  each  essentially 
different  from  the  others,  thus : 


Atoms.          Weight.  Atoms.          Weight.  Gross  Weight. 

1  of  Nitrogen  14  unites  with  1  of  Oxygen  8  forming  Nitrous  Oxide  .  .  22 
"  2  "  16  "  Nitric  Oxide  .  .  30 
"  3  "  24  "  Hyponitrous  Acid  38 
"  4  «  32  «  Nitrous  Acid  .  .46 
"  5  «  40  "  Nitric  Acid.  .54 


14 
14 
14 
14 


Or  thus : 


...Atmospheric  Air. 


Nitrous  Oxide. 


.Nitric  Oxide. 


Hyponitrous  Acid. 


Nitrous  Acid. 


Nitric  Acid. 


140  HEATING. 

A  description  of  the  properties  of  these  distinct  bodies  may  be 
found  in  any  chemical  work  of  authority,  and  I  only  mention 
these  unions  to  exemplify  the  importance  of  attending  to  the 
proportions  in  which  bodies  unite ;  as  we  here  find  the  very  ele- 
ments of  the  air  we  breathe,  by  a  mere  change  in  the  proportions 
in  which  they  are  united,  forming  so  many  distinct  substances, 
from  the  laughing  gas,  nitrous  oxide,  up  to  that  most  powerful 
and  destructive  agent,  nitric  acid,  commonly  called  aqua-fortis. 

This  case  of  the  combination  of  nitrogen  and  oxygen  also 
shows  the  importance  of  the  distinction  between  mechanical  and 
chemical  union ;  these  two  elements  being  only  mechanically 
united  in  forming  atmospheric  air,  by  which  the  essential  prop- 
erties of  its  two  constituents  as  preserved  unaltered ;  whereas, 
in  the  five  bodies  above  enumerated,  the  union  is  chemical,  and, 
consequently,  the  essential  characters  of  their  respective  con- 
stituents are  lost,  and  new  ones  obtained. 

Now,  to  apply  these  principles  to  the  bodies  under  considera- 
tion, namely,  the  carbon  and  hydrogen,  and  ascertain  the  propor- 
tions of  oxygen  they  respectively  require  to  produce  chemical 
union. 

These  two  constituents,  though  united  in  the  one  body  —  the 
gas  —  yet,  not  only  separate  themselves  during  combustion  in  a 
remarkable  manner,  but,  by  two  distinct  processes,  form  two  essen- 
tially different  unions.  This  is  an  important  feature  of  the 
development  of  chemical  action  which  the  law  of  equivalents  at 
once  points  out  and  enables  us  to  satisfy,  although  this  double 
process  does  not  appear  to  be  understood,  much  less  to  be  pro- 
vided for,  in  practice,  though  familiar  to  every  chemist. 

On  the  first  application  of  heat,  or  what  may  properly  be 
termed  the  firing  or  lighting  the  gas,  when  duly  mixed  with  air, 
the  carbon  separates  itself  from  its  fellow-constituent,  the  hydro- 
gen,  and  forms  a  union  with  the  former,  the  produce  of  which 
is  carbonic  acid  gas. 

Now,  the  laws  of  chemical  proportion  teach  us  that  carbonic 
acid  is  composed  of  one  atom  of  carbon  vapor,  (by  weight  6,) 
and  two  atoms  of  oxygen,  (by  weight  16,)  the  latter,  in  volume, 
being  double  that  of  the  former,  as  in  the  annexed  figure  : 


PRINCIPLES    OF    COMBUSTION.  141 


Carbonic  acid. 


Thus,  as  far  as  the  carbon  is  concerned,  we  obtain  the  infor- 
mation we  sought,  namely,  its  saturating  equivalent  of  oxygen, 
and  which  we  find  to  be  just  double  its  own  volume ;  or,  by 
weight,  as  16  is  to  6.  But,  without  the  aid  of  chemistry,  we 
should  here  have  remained  satisfied  ;  combustion  would  appear 
to  have  been  complete ;  there  would  be  no  smoke,  and  no  visi- 
ble indication  of  an  imperfect  or  unfinished  process.  Yet,  chem- 
istry tells  us,  we  have  only  disposed  of  the  one.  constituent  of 
the  gas,  namely,  the  carbon,  and  that  the  hydrogen,  the  second 
constituent,  remains  yet  to  be  accounted  for,  and  converted  to 
heating  purposes.  * 

It  is  true,  the  carbon  was,  in  weight,  equal  to  six  parts  out  of 
eight  (the  original  weight  of  the  gas.)  In  bulk,  however,  it  was 
but  one  fifth;  and  when  it  is  recollected,  that,  although  the 
illuminating  properties  of  the  carbon  are  superior  to  those  of  the 
hydrogen,  yet  that  the  heating  properties  of  the  hydrogen  are 
far  superior  to  those  of  the  carbon,  we  can  appreciate  the  loss  sus- 
tained should  these  four  fifths  of  the  gas  remain  unconsumed. 

To  this  may  be  added,  the  probable  injury  done  to  the  heat- 
ing powers  of  the  flame  by  the  conversion  of  any  part  of  this 
otherwise  valuable  hydrogen  into  one  of  the  most  destructive 
compounds  which  can  be  met  with  in  the  furnace  or  flues, 

*  I  have  here  stated  the  case  of  the  oxygen  uniting  with  the  carbon, 
before  the  hydrogen.  Chemists  are  undecided  on  this  point ;  and,  indeed, 
the  evidence  at  present  is  quite  contradictory. 

It  is  to  be  observed,  however,  that  the  argument,  drawn  from  the 
combustion  of  the  carbon  before  the  hydrogen,  or  vice  versa,  is  the  same, 
as  regards  the  point  now  under  consideration.  Whichever  half  passes 
off  uncombined,  is  lost. 


142  HEATING. 

namely,  ammonia,  composed  of  unconsumed  hydrogen  and  a 
portion  of  the  nitrogen  liberated  from  the  air.  Thus  we  have  a 
double  motive  for  providing  against  the  escape,  unconsumed,  of 
the  hydrogen  of  the  gas. 

What,  then,  is  to  be  done  ?  Let  us  complete  this  second 
process  as  we  did  the  first :  let  us  supply  this  hydrogen,  this 
remaining  80  per  cent,  in  volume  of  the  gas,  with  its  own  proper 
equivalent  of  oxygen,  as  we  did  in  the  case  of  the  carbon. 

But  what  is  this  second  equivalent  ?  By  the  same  laws  of 
definite  proportions,  we  learn  that  the  saturating  equivalent  of 
an  atom,  or  any  other  given  quantity  of  hydrogen,  is,  not  double 
the  volume,  as  in  the  case  of  the  carbon,  but  one  half  its  volume 
only  —  the  product  being  aqueous  vapor,  that  is,  steam ;  the 
relative  weights  of  the  combining  volumes  being  1  of  hydrogen 
to  8  of  oxygen ;  and  the  bulk,  when  combined,  being  two  thirds 
of  the  bulk  of  both  taken  together,  as  shown  in  the  annexed 
figure  8.  * 

We  thus  find,  that  to  saturate  the  one  volume  of  carbon  vapor, 
two  volumes  of  oxygen  are  required ;  whereas,  to  saturate  the 
two  volumes  of  hydrogen,  one  volume  only  of  oxygen  is  required : 
thus, 

FIRST   CONSTITUENT. 
Carbon.  Oxygen. 

Vol.  Atom.  Weight.  Vol.  Atom.  Weight.  Vol.  Atom.  Weight. 

1  .    .  1  .    .    .6  unite  with  1  .    .  2  .    .    .16  forming  )  .         l  22 

carbonic  acid.    ) 

SECOND   CONSTITUENT. 
Hydrogen.  Oxygen. 

Vol.  Atom.  Weight.  Vol.  Atom.    Weight.  Vol.  Atom.  Weight. 

2  .   .  2  .    .    .2  unite  with  1  .   .  2  .    .   .16  forming  )  0        0 

steam,    j2'    '2'   '   '  18 

Here  we  see,  that,  in  the  case  of  this  first  constituent,  as 
above,  the  half  volume  of  carbon  and  one  volume  of  oxygen 

*  Professor  Brande  puts  this  so  clearly  that  I  here  give  his  own 
words  :  —  "  The  simple  ratio  which  the  weights  of  the  combining  ele- 
ments bear  to  each  other  involves  an  equally  simple  law  in  respect  to 
combining  volumes,  where  substances  either  exist,  or  may  be  supposed 
to  exist,  in  the  state  of  gas  or  vapor. 

"  Thus,  water  may  be  considered  as  a  compound  of  1  atom  of  hydro- 
gen and  1  atom  of  oxygen,  the  relative  weights  of  which  are  to  each 


PRINCIPLES    OF    COMBUSTION. 


143 


become  condensed  into  one  volume  of  carbonic  acid  (as  shown  in 
the  last  figure) ;  and  that,  in  the  second  constituent,  the  two  vol- 
umes (meaning  double  bulk)  of  hydrogen,  and  one  volume  of 
oxygen,  become  condensed  into  two  volumes  of  steam,  (as 
shown  in  the  annexed  figure.) 

other  as  1  to  8.  Hence,  the  equivalent  of  the  atom  of  water  will  be,  1 
hydrogen  -f-  8  oxygen  =  9.  But  oxygen  and  hydrogen  exist  in  the  gase- 
ous state,  and  the  weight  of  equal  volumes  of  those  gases  (or,  in  other 
words,  their  relative  densities,  or  specific  gravities)  are  to  each  other  as 
1  to  16 ;  hence,  1  volume  of  hydrogen  is  combined  with  £  a  volume  of 
oxygen  to  form  1  volume  of  the  vapor  of  water,  or  steam :  for  the  specific 
gravity  of  steam,  compared  with  hydrogen,  is  as  1  to  9.  The  annexed 
diagram,  therefore,  will  represent  the  combining  weights  and  volumes  of 
the  elements  of  water  and  of  its  vapor." 


Hydrogen,  1. 

= 

Steam,  9. 

Oxygen,  8. 

Steam. 


or  thus, 


The  following  is  also  much  to  the  point :  —  "La  composition  de  1'eau 
cst  un  des  elemens  les  plus  necessaires  aux  calculs  des  chemistes,  les 
derniers  experiences  de  MM.  Berzelius  et  Dulong  out  fourni  pour  sa 
composition  des  nombres  qui  sont  adoptes  t>ar  t.ous  les  chemistes.  Elle 
est  formee  d'apres  eux  de 

Oxygene 88.90 1  volume,  oxygene. 

Hydrogene  .   .   .   .11.10 2  volumes,  hydrogene. 

100.00  1  volume  eau. 

Parmi  les  nombreuses  decouvertes  que  la  science  doit  a  M.  Gay  Lussac, 
on  remarquera  toujours  la  belle  observation  sur  la  composition  de  1'eau, 
qui  le  conduisit  a  trouver  les  vrais  rapports  des  gaz  et  des  vapeurs  dans 
leurs  combinaison.  Des  experiences  tres  exactes,  qu'il  avoit  faites  con- 
jointement  avec  M.  de  Humboldt,  lui  prouverent  que  Ve.au  formee  (Pun 
volume  d'oxygene  et  de  deux  volumes  de  hydrogene,  resultat  plainement 
confirme  depuis  par  tous  les  phenomenes  ou  1'eau  joue  un  role  actif,  et 
qui  s'accorde  avec  la  composition  trouve  par  MM.  Berzelius  et  Dulong." 
—  Dumas,  vol.  i.,  p.  33. 

13 


144  HEATING. 

No  facts  in  chemistry,  therefore,  can  be  more  decidedly 
proved,  than  that  one  atom  of  hydrogen  and  one  atom  of 
oxygen  (the  former  being  double  the  bulk  of  the  latter)  unite  in 
the  formation  of  water;  and,  further,  that  one  atom  of  carbon 
vapor  and  two  atoms  of  oxygen  (the  latter  being  double  the  bulk 
of  the  former)  unite  in  the  formation  of  carbonic  acid  gas. 

Thus,  the  ultimate  fact  of  which  we  were  in  search  is,  that 
the  one  condensed  volume  of  the  gas,  as  generated  from  the 
coal,  requires  two  volumes,  or  double  its  bulk  of  oxygen,  that 
being  the  quantity  required  for  the  saturation  of  its  constituents 
when  separated. 

Now,  this  is  the  entire  alphabet  of  the  combustion  of  the  car- 
buretted  hydrogen  gas. 

Having  thus  ascertained  the  quantity  of  oxygen  required  for 
the  saturation  and  combustion  of  the  two  constituents  of  coal 
gas,  the  only  remaining  point  to  be  decided  is,  the  quantity  of 
air  that  will  be  required  to  supply  this  quantity  of  oxygen. 

This  is  easily  ascertained,  seeing  that  we  know  precisely  the 
proportion  which  oxygen  bears,  in  volume,  to  that  of  the  air. 
For,  as  the  oxygen  is  but  one-fifth  of  the  bulk  of  the  air,^ne 
volumes  of  the  latter  will  necessarily  be  required  to  produce  one 
of  the  former ;  and,  as  we  want  tivo  volumes  of  oxygen  for  each 
volume  of  the  coal  gas,  it  follows,  that  to  obtain  those  two  vol- 
umes, we  must  provide  ten  volumes  of  air. 

Thus,  then,  by  strict  chemical  proof,  we  have  obtained  these 
facts  :  —  First,  that  each  volume  of  coal  gas  requires  two  vol- 
umes of  oxygen ;  secondly,  that  to  obtain  these  two  volumes  of 
oxygen  we  must  employ  eight  atoms  of  air ;  thirdly,  that  these 
eight  atoms  of  air  are  equal  to  ten  volumes  of  the  coal  gas ; 
each  volume  of  the  latter,  in  fact,  requiring  ten  volumes,  or  ten 
times  its  bulk  of  air  :  thus, 

Ten  volumes  of  air  are  the  same  as  eight  atoms  ; 

Eight  atoms  of  air  produce  four  atoms  of  oxygen ; 

Four  atoms  of  oxygen  are  equal  to  two  volumes  of  the  same  ;  and 

Two  volumes  of  oxygen  saturate  one  volume  of  the  coal  gas  : 

Therefore,  ten  volumes  of  air  are  required  for  each  one  volume  of  this  gas. 

We  now  see  why  ten  volumes  of  air  are  required  for  each 


PRINCIPLES    OF   COMBUSTION.  145 

volume  of  gas,  and  why  neither  more  nor  less  will  satisfy  the 
conditions  of  its  combustion.  For,  if  more,  the  excess,  inde- 
pendently of  the  mischievous  chemical  unions  that  might  enter 
into  it  in  the  furnace,  would  be  the  means  of  carrying  away  as 
much  heat  as  it  would  take  up  by  its  expanding  faculty.  And 
if  less,  a  corresponding  quantity  of  either  hydrogen  or  carbon 
would  be  deficient  of  its  supporter,  and  necessarily  pass  off 
uncombined  and  unconsumed. 

The  only  observation  here  necessary  to  make  on  the  difference 
between  these  two  gases  is,  that  as  this  latter  gas  contains  two 
atoms  of  carbon  instead  of  one,  it  follows  that  a  proportionate 
additional  quantity  of  oxygen  will  be  required  for  this  additional 
atom  of  carbon.  Hence,  if  carburetted  hydrogen  requires  two 
volumes  of  oxygen  for  combustion,  the  bi-carburetted  hydrogen 
will  require  three  volumes.  And  so  of  air :  if  ten  volumes  of 
air  are  required  for  the  one  gas,  fifteen  volumes  are  consequently 
required  for  the  other  gas. 

4.  We  have  seen  that,  in  the  formation  of  the  carburetted 
hydrogen,  a  considerable  portion  of  the  carbonaceous  constituent 
of  fuel  is  separated,  and  carried  away  by  the  hydrogen  in  the 
gaseous  form,  forming  the  carburetted  hydrogen  ;  the  remainder 
of  such  carbonaceous  matter  is  what  we  have  now  to  deal  with ; 
the  difference  as  regards  combustion  between  these  two  portions 
of  carbon  being  so  important  as  to  demand  especial  notice. 

In  observing  this  curious  arrangement  by  which  the  saturation 
of  the  combustible  atoms  is  effected,  we  perceive  that  three  atoms 
of  the  combustible  are  apportioned  to  four  of  the  supporter. 
This,  we  see,  is  the  result  of  one  atom  of  carbon  requiring  two 
of  the  supporters,  while  the  two  of  hydrogen  are  satisfied  with 
one  each. 

Now,  in  this  arrangement  no  excess  or  deficiency  appears 
among  the  heat-producing  ingredients.  Could  we  have  dis- 
pensed with  or  avoided  the  presence  of  such  an  excess  of  nitro- 
gen, (which  is  neither  a  combustible  nor  supporter  of  combus- 
tion,) the  several  unions  would  have  been  less  embarrassed,  — 
their  combustion  more  rapid  and  complete,  —  and  the  intensity 
of  their  action  much  increased.  That,  however,  was  impossible. 


146  HEATING. 

The  presence  of  so  large  a  quantity  of  nitrogen  being  the  una- 
voidable condition  of  obtaining  the  oxygen  through  the  instru- 
mentality of  atmospheric  air, 

It  is  to  be  observed  that  the  process  of  combustion  here 
described  is  the  most  perfect  that  could  be  produced,  either  in  a 
furnace  or  lamp.  Any  deviation,  therefore,  by  means  of  excess 
or  deficiency,  or  from  any  interruption  or  interference,  such  as 
the  interposition  of  another  gas,  must  be  more  or  less  destructive 
to  the  desired  effect,  viz.,  the  generation  of  the  greatest  quantity 
of  available  heat. 

5.  When  we  speak  of  mixing  a  given  quantity  of  oxygen 
with  a  given  volume  of  smoke,  (or  coal  gas,)  we  do  so  because 
we  know  that  such  quantity  of  the  former  is  required  to  saturate 
the  latter,  and  by  such  saturation  every  atom  of  loth  gases 
enters  into  union,  without  excess  or  deficiency  of  either,  pro- 
ducing entire  and  complete  combustion. 

So,  when  we  speak  of  mixing  a  given  volume  of  atmospheric 
air  with  a  given  volume  of  smoke,  we  do  so  for  the  same  pur- 
pose, knowing  that  the  precise  quantity  of  air  will  provide  the 
required  quantity  of  oxygen. 

Thus,  if  we  know  that  two  cubic  feet  of  oxygen  are  the  exact 
saturating  equivalent,  or  combining  volume,  for  effecting  the  en- 
tire combustion  of  one  cubic  foot  of  coal  gas,  we  know  that  ten 
cubic  feet  of  atmospheric  air  will  effect  the  same  purpose, 
because  ten  cubic  feet  of  air  contain  the  required  two  cubic  feet 
of  oxygen. 

We  require  ten  cubic  feet  of  air  to  supply  two  cubic  feet  of 
oxygen,  which,  if  the  air  be  pure,  effects  the  combustion  of  one 
cubic  foot  of  coal  gas,  emanating  from  coals  in  the  process  of 
combustion  in  a  furnace ;  but  if  this  quantity  of  air  does  not 
contain  this  20  per  cent.,  or  one-fifth,  of  oxygen,  it  is  clear  we 
cannot  obtain  it.  The  air,  in  this  case,  may  be  said  to  be  viti- 
ated, or  impure.  It  is  therefore  desirable  that  the  air  admitted 
into  a  furnace  should  be  direct  from  the  atmosphere ;  otherwise, 
the  oxygen  contained  may  be  deficient,  although  the  volume 
of  air  admitted  be  sufficiently  large. 


PRINCIPLES    OF    COMBUSTION.  147 

Let  us  now  inquire  how  far  the  ordinary  mode  of  constructing 
and  managing  our  furnaces  enables  us  to  satisfy  this  condition. 

In  ordinary  furnaces,  the  supply  of  air  is  obtained  by  means 
of  the  ash-pit ;  and  the  larger  the  ash-pit,  the  greater  the  quan- 
tity of  air  admitted.  The  ash-pit  is  made  larger,  under  the 
mistaken  notion  that  the  more  air  we  give,  the  better  will  be  the 
draught,  the  more  complete  the  combustion,  and  the  greater  the 
quantity  of  heat  produced. 

There  can  scarcely  be  a  more  absurd  practice  than  is  involved 
in  this  one-sided  view  of  the  principles  of  combustion,  even  sup- 
posing that  the  introduction  of  air  is  tantamount  to  the  introduc- 
tion of  oxygen.  It  is  manifest,  however,  that  there  are  two 
different  processes  going  on  in  the  furnace,  and  two  different 
combustibles,  requiring  their  respective  volumes  of  oxygen  to 
consume  them,  namely,  the  gas  or  smoke  generated  in  the  body 
or  cavity  of  the  furnace,  and  passing  off  by  the  flues,  and  also, 
the  solid  carbon  resting  on  the  bars,  both  of  which  require  sepa- 
rate volumes  of  oxygen  to  effect  their  combustion. 

All  that  seems  to  be  concluded  in  practice  is,  that  air  is 
essential  to  combustion ;  and  that  if  air  be  admitted  to  the  fuel, 
through  between  the  bars,  it  will  work  out  the  process  of  com- 
bustion satisfactorily  in  its  own  way.  And  hence  the  many 
errors  and  absurdities  of  the  present  system  of  practice. 

There  can  be  no  greater  mistake  than  letting  a  large  quantity 
of  air  act  directly  on  the  burning  fuel,  which  acts  like  a  blast 
upon  the  red-hot  mass,  driving  off  the  gases  more  rapidly,  but 
also  driving  off  the  contained  heat,  and  consuming  the  fuel  with 
unnecessary  rapidity. 

It  seems  to  be  taken  for  granted,  that  if  air,  by  any  means,  be 
introduced  to  the  fuel  in  the  furnace,  it  will,  as  a  matter  of 
course,  mix  with  the  gas,  or  other  combustible,  in  a  proper  man- 
ner, and  assume  the  state  suitable  for  combustion,  whatever  be 
the  nature  or  state  of  such  fuel,  and  without  regard  to  time  or 
other  circumstances.  Now,  it  might  as  well  be  supposed,  that 
by  bringing  large  masses  of  nitre,  sulphur,  and  charcoal  to- 
gether, we  could  form  gunpowder.  We  know  that  it  is  by  the 
proper  mixture  and  incorporation  of  the  different  elementary 
atoms  that  simultaneous  action  is  imparted  to  the  whole ;  and 
13* 


148  HEATING. 

so,  also,  by  bringing  different  kinds  of  gases  into  a  state  of 
preparation  for  simultaneous  action. 

The  complete  combustion  of  a  body  depends  upon  the 
chemical  union  of  its  atoms,  or  elementary  divisions,  with  their 
respective  equivalents  of  the  supporter,  oxygen;  and  which 
necessarily  implies  the  bringing  together,  and  the  mixing  of 
such  atoms,  previous  to  the  mixture  being  fired  for  combustion. 

It  is  not  our  purpose  to  enter  upon  the  theory  of  atomic  mix- 
tures, or  the  time  required  to  effect  their  combination,  —  which 
will  be  found  in  the  numerous  chemical  works  of  the  present 
day.  We  will  now  proceed  to  consider  the  means  by  which  air 
may  be  introduced  to  the  furnace,  to  effect  the  combustion  of  the 
gases  therein  generated. 

In  looking  for  a  remedy  for  the  evils  arising  out  of  the  hurried 
state  of  things  which  the  interior  of  a  furnace  naturally  presents, 
and  observing  the  means  by  which  the  gas  is  effectually  con- 
sumed in  the  Argand  lamp,  it  seemed  manifest,  if  the  gas  in  the 
furnace  could  be  presented  by  means  of  jets  to  an  adequate 
quantity  of  air,  as  it  is  in  the  lamp,  the  result  would  be  the 
same,  —  namely,  a  quicker  and  more  intimate  mixture  and  diffu- 
sion, and  consequently  a  more  extensive  and  perfect  combustion. 
The  difficulty  of  effecting  a  similar  distribution  of  the  gas  in 
the  furnace,  by  means  of  jets,  however,  seems  insurmountable. 
One  alternative  alone  remains :  since  the  gas  cannot  be  intro- 
duced by  jets  into  the  body  of  the  air,  the  air  might  be  intro- 
duced by  jets  into  the  body  of  the  gas ;  and  this  will  be  an 
effectual  remedy. 

FIG.  33  is  a  section  of  Williams'  furnace  for  the  prevention 
of  smoke.  In  this  furnace,  the  fuel,  as  will  be  seen  from  the 
cut,  is  thrown  immediately  upon  the  grate  bars,  and  through 
them  the  air  finds  admission  to  it  for  the  purpose  of  consump- 
tion. The  gases  pass  over  the  bridge  C ;  here  they  meet  a  cur- 
rent of  air  entering  just  beyond  the  bridge,  which  has  been 
admitted  by  the  air-tube  £,  below  the  ash-pit  /,  into  the  air- 
chamber  d,  and  from  thence  escaping  through  a  great  number 
of  small  apertures  in  the  diffusion  plate  above. 

The  force  with  which  the  air  enters  through  this  series  of 
jets  or  blow-pipes  enables  it  to  penetrate  into  the  gases,  and 


HEATING. 


149 


150  HEATING. 

obtain  the  largest  possible  extent  of  contact-surfaces  for  the  air 
and  gases ;  which  is  important,  since  the  short  time  allowed  for 
the  diffusion  would  otherwise  be  insufficient,  in  consequence  of 
the  rapid  passage  of  the  smoke  and  gases  over  the  diffusion 
plates ;  e  is  the  spy-hole  for  ascertaining  the  state  of  the  smoke. 

FIG.  34  is  an  apparatus  invented  by  Mr.  Jeffreys,  of  Bristol,  as 
long  ago  as  1824,  for  precipitating  the  lamp-black,  metallic 
vapors,  and  other  sublimated  matters  from  smoke,  by  washing 
the  latter  by  means  of  a  stream  of  water.  Where  the  necessary 
supply  can  be  secured,  this  plan  is  both  effectual  and  economi- 
cal, and  well  adapted  for  situations  where  the  presence  of  smoke, 
as  well  as  the  impurities  produced  by  it,  is  an  annoyance. 

In  the  vertical  section,  B  B  is  the  smoke  flue.  The  smoke 
passing  in  the  direction  of  the  arrows  at  A,  the  flue  turns  down- 
ward; and  at  the  top  of  this  vertical  portion  is  a  cistern  E,  the 
perforated  bottom  of  which  lets  down  a  constant  stream  of 
water,  after  it  is  set  to  work.  The  shower,  in  its  descent,  carries 
all  the  smoke  and  the  sublimated  matter  which  has  passed  from 
the  fire,  which  runs  off  at  the  bottom,  F.  The  flue  may  then 
turn  upwards,  or  enter  a  common  chimney ;  but  little  or  nothing 
will  pass  up  it,  providing  the  water  be  kept  constantly  running. 
This  apparatus  is  easily  constructed,  and  is  admirably  suited  for 
hot-houses  situated  in  the  midst  of  pleasure-grounds,  where 
smoke  is  unsightly  and  disagreeable. 

Whether  these  methods  of  consuming  the  gases  generated  in 
the  furnaces  and  flues  of  hot-houses  may  be  considered  worthy 
of  general  adoption,  we  cannot  tell.  It  is,  nevertheless,  pre- 
sented to  the  consideration  of  the  ingenious  mechanic,  not 
doubting  that  were  the  subject  fully  taken  up  by  energetic  fur- 
nace builders,  something  good  would  be  the  result.  That 
immense  quantities  of  fuel  are  wasted  by  imperfect  combustion, 
cannot  be  doubted,  when  we  see  the  dense  volumes  of  smoke 
proceeding  from  chimneys  where  much  heat  is  required. 

Professor  Brande  says,  "  when  air  is  admitted  in  front  of  the 
furnace,  or  through  or  over  the  fuel,  it  obviously  never  can 
effect  those  useful  purposes,  which  are  at  once  obtained  by 
admitting  it  in  due  proportion  to  the  intensely  heated  inflamma- 
ble vapors  and  gases,  or,  in  other  words,  to  the  products  of  the 


HEATING. 


151 


Fig.  34. 


152  HEATING. 

distillation  of  coal,  at  such  temperatures  that  they  may  take  fire 
in  its  contact."  If  a  number  of  jets  of  air  be  admitted  into  a 
heated  inflammable  atmosphere,  as  the  body  of  a  furnace,  its 
combustion  will  be  attained  in  such  a  way  as  to  produce  a  great 
increase  of  heat,  and,  as  a  necessary  consequence,  destroy  the 
smoke. 

In  some  of  the  large  gardens  of  Europe,  as  well  as  in  some 
manufactories,  attempts  have  been  made  to  consume  the  smoke 
or  gases  of  the  furnaces,  by  bringing  them  in  contact  with  a  body 
of  glowing  incandescent  fuel,  producing  a  result  the  reverse  of 
what  was  expected,  namely,  the  absorption  of  heat  by  their 
expansion  and  decomposition,  instead  of  giving  out  heat  by  their 
combustion.  It  is  strange  that  this  erroneous  notion  should  be 
persisted  in,  even  at  the  present  day,  when  any  chemical  work 
of  good  authority  would  satisfy  any  one  wishing  for  such  knowl- 
edge that  decomposition,  not  combustion,  is  the  effect  of  a  high 
temperature  being  applied  to  hydro-carbon-gases ;  —  that  no 
possible  degree  of  heat  can  consume  carbon  ;  —  that  it  is  a  well- 
known  property  of  both  the  varieties  of  carburetted  hydrogen, 
that  they  deposit  charcoal,  (carbon)  virtually  become  smoke, 
when  heated ;  —  that  the  amount  of  carbon  deposited  is  propor- 
tioned to  the  increase  of  temperature,  and  that  its  combustion  is 
merely  produced  by,  and  is,  in  fact,  its  union  with,  oxygen, 
which  these  smoke-burners  take  no  care  to  provide.^ 

*  Numerous  methods  have  been  devised  for  burning  smoke,  and 
patents  have  been  issued  for  supposed  inventions  of  this  kind,  showing 
the  want  of  chemical  knowledge  on  this  subject.  One  consists  in  hav- 
ing a  double  set  of  fire-bars,  so  that  when  the  fuel  is  red-hot,  it  is 
thrown  back  on  the  innermost  bars,  and  the  smoke  of  the  fresh  coal  in 
front  passing  over  this  incandescent  fuel,  is  supposed  to  be  consumed  in 
its  passage.  Another  proposes  a  sliding  carriage  for  this  purpose, 
working  on  castors  inside  the  furnace.  Others  of  a  similar  kind  have 
been  put  forward,  and  all  on  the  same  principle ;  all  manifesting  the 
same  neglect  or  ignorance  of  chemistry,  —  for  chemistry  teaches  us 
that  heat  has  nothing  to  do  with  the  combustion  of  smoke  beyond  this,  — 
that  a  certain  temperature  is  essential  to  the  development  of  chemical 
action  between  the  combustible  and  the  supporter,  when  they  are 
brought  together.  But  producing  heat  is  not  producing  air ;  and  decom- 
position is  not,  in  this  respect,  combustion. 


PRINCIPLES    OF    COMBUSTION.  153 

The  neglect  of  chemistry  when  treating  of  combustion,  and 
the  results  of  this  neglect  in  these  smoke-burning  furnaces,  can- 
not be  too  strongly  exposed  ;  neither  can  its  study  be  too  strongly 
enforced,  seeing  that  it  is  practically  within  the  reach  of  all. 
For  chemistry  is  no  longer  the  mysterious  alchemy  that  it  was 
a  century  ago  ;  it  is  now  a  mere  rigid  inquiry  into  nature's  pro- 
cesses and  laws,  by  the  aid  of  those  proofs  and  illustrations 
which  nature  herself  has  supplied.  It  has  taken  its  place  among 
the  exact  sciences,  and  now  recognizes  no  man's  dictum  or  opin- 
ion, apart  from  experimental  tests,  and  strict,  substantial  evidence. 

Looking,  then,  to  chemistry,  we  would  add,  in  reference  to 
these  smoke-burning  expedients,  that,  in  seeking  to  obtain  heat 
from  gas,  (or  smoke,)  the  bringing  it  into  connection  with  ignited 
carbonaceous  matter,  or  to  anything  approaching  the  temper- 
ature of  incandescence,  is  absolutely  useless,  if  not  injurious, 
until  we  are  assured  of  having  the  means  of  contact  with  air 
fully  provided  for. 

The  mere  enunciation  of  a  plan  "  for  consuming  smoke"  is 
prima  facie  evidence  that  the  inventor  has  not  studied  and  con- 
sidered the  subject  in  its  chemical  relations.  Chemists  can 
understand  a  plan  for  the  prevention  of  smoke  ;  but  as  to  its 
combustion,  it  is  so  unscientific,  not  to  say  impossible,  (if  there 
be  any  truth  in  chemistry,)  that  such  phraseology  should  be 
avoided.  The  popular  phrase,  "  A  furnace  burning  its  own 
smoke,"  may  be  justifiable,  as  conveying  an  intelligible  mean- 
ing ;  but,  in  a  work  having  any  pretensions  to  science,  or  from 
any  one  pretending  to  teach  those  who  are  unable  to  distinguish 
for  themselves,  and  who  may  easily  be  led  into  error,  is  wholly 
objectionable. 

6.  Construction  of  Furnaces.  —  From  what  has  been  already 
said,  in  the  preceding  part  of  this  section,  it  will  be  seen  that 
the  construction  of  furnaces  is  a  matter  of  great  importance  in 
the  economy  of  heat.  To  investigate  the  various  varieties  of 
furnaces  which  have  been  recommended,  would  occupy  too  much 
of  our  space  at  present,  especially  as  we  shall  have  to  refer  to 
them  hereafter,  when  treating  of  the  different  methods  of  heat- 
ing; besides,  in  small  apparatuses,  the  intense  heat  required 


154  HEATING. 

for  large  boilers  is  unnecessary.  A  very  moderate  heat,  ap- 
plied on  the  most  economical  principle,  and  the  furnace  so  con- 
structed as  to  make  the  fuel  burn  for  a  long  time,  without  much 
attention,  and  without  much  escape  of  smoke,  is  the  grand 
desideratum,  and  which  is  easily  accomplished,  with  a  moderate 
degree  of  care  and  skill  in  the  erection. 

Passing  over,  then,  as  unnecessary  for  our  purpose  at  present, 
the  many  ingenious  forms  which  have  been  given  to  furnaces, 
we  will  proceed  to  describe  the  most  simple  plan,  which,  in  our 
experience,  is  the  most  effectual  in  the  combustion  of  the  fuel, 
as  well  as  the  least  expensive  in  the  construction. 

It  should  be  an  object  of  consideration,  in  building  the  fur- 
nace, to  confine  the  generated  heat  within  the  cavity  of  the 
furnace  as  much  as  possible,  so  that  the  gases  generated  by  the 
combustion  of  fuel  may  be  prevented  from  passing  too  rapidly 
along  the  flue  ;  this  is  more  especially  requisite  with  boiler 
furnaces.  The  throat  of  the  furnace  should  be  contracted  as 
much  as  possible.  In  furnaces  where  the  only  entrance  for  air 
is  by  the  bars,  provision  should  be  made  for  the  entrance  of 
enough  —  but  no  more  than  enough  —  for  the  combustion  of 
the  fuel,  and  the  entrance  should,  in  all  cases,  be  regulated  by 
a  damper,  on  the  ash-pit  door.  It  should  be  considered,  that 
the  rarity  of  the  heated  gases  causes  them  to  force  their  pas- 
sage through  the  throat  of  the  furnace,  just  in  the  proportion 
of  its  size. 

We  have  already  shown  that  any  air  entering  through  the 
door  of  the  furnace  reduces  the  intensity  of  the  heat,  although 
it  is  supposed  by  some  that  the  passage  of  air  over  the  burning 
fuel  promotes  the  more  perfect  combustion  of  the  gaseous  pro- 
ducts of  the  coal.  But  even  if  this  be  correct,  the  heat  will  be 
reduced,  and  less  heat  will  be  generated  in  a  given  time,  than 
if  the  whole  gaseous  products  escaped  by  the  chimney. 

The  kind  of  fuel  to  be  burnt  must,  in  all  cases,  determine 
the  width  of  the  bars ;  and  as  a  certain  open  area  is  necessary 
for  the  admission  of  air  to  effect  combustion,  it  is  desirable  that 
this  area  should  be  known. 

Supposing  the  ordinary  kind  of  furnace  bars  to  afford  about 
thirty  inches  of  opening  for  air  for  every  square  foot  of  surface,  — 


PRINCIPLES    OF    COMBUSTION. 


155 


then  supposing  you  wish  to  erect  a  hot  water  apparatus  —  the 
relative  proportions  between  the  area  of  the  bars  and  the  length 
of  pipe  would  be  as  follows  :  — 


Area  of  Bars. 

75  square  inches  will  supply 
100       "  " 

150       "  " 

200       "  " 

250       "  " 

300       "  " 

400       "  " 

500       "  " 


4  inch  pipe.    3  inch  pipe.    2  inch  pipe. 
150  feet,  or  200  feet,  or  300  feet. 


200 

266 

400  « 

300 

400 

600  " 

400 

533 

800  " 

500 

666 

1000  " 

600 

800 

1200  " 

snn 

mfifi  < 

t    1600  " 

1000 


1333    "         2000    " 


Thus,  suppose  there  are  six  hundred  feet  of  pipe,  four  inches 
in  diameter,  in  an  apparatus,  —  then  the  area  of  the  bars  should 
be  three  hundred  square  inches,  so  that  thirteen  inches  in 
breadth,  and  twenty-three  inches  in  length,  will  give  the  re- 
quired quantity  of  surface.  When  it  is  required  to  obtain  the 
greatest  heat  in  the  shortest  time,  the  area  of  the  bars  may  be  a 
little  increased. 

In  order  to  make  the  fire  burn  for  a  long  time  without  atten- 
tion, the  furnace  should  extend  beyond  the  bars,  both  in  length 
and  breadth ;  and  the  coals,  which  are  placed  on  this  blank  part 
of  the  furnace,  in  consequence  of  receiving  no  air  from  below, 
will  burn  slowly,  and  will  only  enter  into  complete  combustion 
when  the  rest  of  the  coal,  on  the  bars,  has  been  consumed. 

It  may  be  observed,  that  as  the  maximum  effect  of  the  furnace 
is  seldom  required,  the  register  on  the  ash-pit  door,  and   the 
damper  in  the  flue,  must  be  used  to  regulate  the  draught,  and 
thus  limit  the  consumption  of  fuel. 
14 


SECTION    II. 

PRINCIPLES     OF     HEATING     HOT-HOUSES. 

1.  Effects  of  artificial  heat.  —  The  effects  that  are  produced 
upon  the  functions  of  vegetables,  by  atmospheric  air  that  has 
passed  over  intensely  heated  surfaces,  are  perceptible  to  the 
most  casual  observer.  The  changes,  therefore,  that  are  produced 
upon  atmospheric  air  by  subjecting  it  to  a  high  temperature,  are 
of  the  utmost  importance  to  the  horticulturist,  and  consequently 
demand  our  particular  attention. 

When  common  air  passes  over  highly  heated  surfaces,  the 
small  particles  of  animal  and  vegetable  matter,  (organic  mat- 
ter,) which  are  always  held  in  suspension  by  it,  are  decomposed 
by  the  heat,  and  resolved  into  various  elementary  gases.  This 
is  one  of  the  causes  of  the  unpleasant  smell  which  results  from 
this  method  of  heating,  as  in  common  stoves,  Polmaise  furnaces, 
&c.  But,  in  addition  to  this,  the  aqueous  vapors  of  the  atmos- 
phere are  almost  entirely  decomposed,  the  oxygen  entering  into 
combination  with  the  iron,  and  the  hydrogen  mixing  with  the 
air.  The  changes  which  have  thus  taken  place,  render  the 
atmosphere  extremely  deleterious  to  both  animal  and  vegetable 
life. 

The  mixture  of  the  hydrogen  thus  disengaged  is  even  more 
injurious  to  the  plants  than  the  alteration  which  has  taken  place 
in  its  hygrometric  state,  as  this  will  be  partly  supplied  by  the 
moisture  contained  in  their  tissue,  until  it  be  restored  to  the 
atmosphere  by  evaporation,  which  is  easily  effected. 

The  particles  of  animal  and  vegetable  matter  —  as  we  have 
said  —  are  decomposed  by  the  heat;  and  they  then  produce 
extraneous  gases,  consisting  of  sulphuretted,  phosphuretted,  and 
carburetted  hydrogen,  with  various  compounds  of  nitrogen  and 


PRINCIPLES    OF    HEATING    HOT-HOUSES.  157 

carbon,  which,  in  the  state  in  which  they  exist,  are  highly  inim- 
ical to  vegetable  life.  * 

The  quantity  of  hydrogen  which  is  eliminated  by  the  decom- 
position of  water  contained  in  the  air  is  one  thousand  three  hun- 
dred and  twenty-five  cubic  inches  for  every  cubic  inch  of  water 
that  is  decomposed ;  and  if  the  dew  point  of  the  air  be  45°  at  an 
average,  this  quantity  will  be  given  out  from  every  seventy-two 
cubic  feet  of  air  wliich  passes  over  the  heated  surface.  It  is, 
therefore,  not  difficult  to  account  for  the  effects  produced  on 
vegetation  by  hot-air  stoves,  in  consequence  of  the  air,  when 
thus  artifically  dried,  abstracting  too  much  moisture  from  their 
leaves.  It  is  also  clear  that  the  injury  must  increase  in  propor- 
tion to  the  length  of  time  the  apparatus  continues  in  use,  by  the 
plants  being  surrounded  by,  and  compelled  to  inhale,  these  extra- 
neous gases,  which  are  evolved  from  the  decomposition  of  the 
constituents  of  the  atmosphere. 

The  extreme  dryness  of  the  air,  after  it  has  been  deprived  of 

*  I  am  unable  to  ascertain  the  exact  nature  and  extent  of  the  change 
which  atmospheric  air  undergoes  by  being  passed  over  intensely  heated 
metallic  bodies  j  but  whatever  be  the  chemical  alteration  which  occurs, 
a  physical  change  undoubtedly  takes  place,  by  which  its  electrical  con- 
dition is  altered. 

From  some  experiments  recorded  in  the  Philosophical  Transactions  of 
the  Royal  Society,  made  with  a  view  of  ascertaining  the  effect  produced 
on  the  animal  economy  by  breathing  air  which  has  passed  through 
heated  media,  it  appears  that  the  air  which  has  been  heated  by  metallic 
surfaces  of  a  high  temperature  must  needs  be  exceedingly  unwholesome. 
A  curious  circumstance  is  related,  in  reference  to  these  experiments, 
which  is  illustrative  of  this  fact. 

"  A  quantity  of  air,  which  had  been  made  to  pass  through  red-hot 
iron  and  brass  tubes,  was  collected  in  a  glass  receiver,  and  allowed  to 
cool.  A  large  cat  was  then  plunged  into  this  air,  and  immediately  she 
fell  into  convulsions,  which,  in  a  minute,  appeared  to  have  left  her 
without  any  signs  of  life ;  she  was,  however,  quickly  taken  out  and 
placed  in  the  fresh  air,  when,  after  some  time,  she  began  to  move  her 
eyes,  and,  after  giving  two  or  three  hideous  squalls,  appeared  slowly  to 
recover.  But  on  any  person  approaching  her,  she  made  the  most  violent 
efforts  her  exhausted  strength  would  allow  to  fly  at  them ;  insomuch, 
that,  in  a  short  time,  no  one  could  approach  her.  In  about  half  an  hour 
she  recovered,  and  became  as  tame  as  before." 


158  PRINCIPLES    OF    HEATING   HOT-HOUSES. 

its  hygrometric  vapor  by  passing  over  a  hot-air  stove,  such  as 
polmaise,  is  productive  of  the  worst  consequences  to  growing 
plants.  To  remedy  this  evil,  a  trough  of  water  is  laid  over  the 
heating  surface,  which  in  some  degree  mitigates  this  evil.  The 
evil,  however,  cannot  be  entirely  got  rid  of  by  this  means ;  for 
even  if  the  proper  quantity  of  moisture  can  be  again  restored  to 
the  air,  the  effects  which  result  from  the  use  of  extraneous 
gases  are  in  no  way  removed.  When  the  surface  of  radiation  is 
an  iron  plate,  these  injurious  effects  are  much  greater. 

The  heating  by  means  of  brick  flues  is,  in  some  respects, 
similar  to  the  effects  produced  by  hot-air  stoves,  but  only  when 
the  flues  are  heated  to  a  high  temperature,  which  is  unneces- 
sary. In  the  latter  case,  an  unwholesome  smell  is  also  produced, 
by  the  decomposition  of  the  organic  matter  in  the  atmosphere, 
and  in  some  cases,  probably,  by  a  small  portion  of  sublimed 
sulphur  from  the  bricks,  as  well  as  by  the  escape  of  various 
gases  through  the  joints  or  accidental  fissures  of  the  flues. 
These  contingent  causes  may,  however,  be  in  a  great  measure 
avoided.  The  hygrometric  vapors  of  the  atmosphere  are  not 
decomposed  by  this  system  of  heating,  as  by  a  hot-air  stove, 
because  when  the  flues  are  warmed  to  a  common  temperature, 
the  heat  is  perfectly  pure,  and  the  materials  of  which  the  flues 
are  built  having  but  little  affinity  for  oxygen,  they  are  conse- 
quently more  healthy  than  hot-air  stoves. 

Air  passing  over  a  highly  heated  surface  of  iron  is,  therefore, 
more  injurious  than  when  passed  over  any  other  body,  as  stone, 
or  brick,  as  the  power  of  iron  to  decompose  water  increases  with 
the  temperature  to  which  it  is  heated.  The  limit  to  which  the 
temperature  of  any  metallic  surface  ought  to  be  raised,  for  warm- 
ing horticultural  buildings,  (or  indeed  any  other  buildings,)  is 
212°,  if  a  healthy,  uncontaminated  atmosphere  be  desired.  The 
importance  of  this  rule  cannot  be  too  strongly  insisted  on,  for 
upon  it  entirely  depends  the  healthiness  of  every  system  of 
artificial  heat. 

2.  Laws  of  Heat.  —  Heated  bodies  give  off  their  caloric  by 
two  distinct  methods  —  radiation  and  conduction.  These  are 
governed  by  different  laws  ;  but  the  rate  of  cooling  —  or  parting 


PRINCIPLES    OF    HEATING    HOT-HOUSES.  159 

with  heat  —  by  both  modes,  increases  in  proportion  as  the 
heated  body  is  of  greater  temperature  above  the  surrounding 
medium. 

The  cooling  of  a  heated  body,  under  ordinary  circumstances, 
is  evidently  the  combined  effects  of  radiation  and  conduction ; 
the  conductive  power  of  the  air  is,  evidently,  owing  to  the  ex- 
treme mobility  of  its  particles,  for  otherwise  it  is  one  of  the 
worst  conductors  with  which  we  are  yet  acquainted,  so  that 
when  confined  in  such  a  manner  as  to  prevent  its  freedom  of 
motion,  it  becomes  useful  as  a  non-conductor. 

The  proportion  which  radiation  and  conduction  bear  to  each 
other  has,  in  general,  been  very  erroneously  estimated.  Count 
Rumford  considered  the  united  effect,  compared  with  radiation 
alone,  was  as  five  to  three,  and  Franklin  supposed  it  to  be  as 
five  to  two. 

No  such  general  law,  however,  can  be  deduced,  for  the  relative 
proportions  vary  with  the  temperature,  and  with  the  peculiar 
substance,  or  surface,  of  the  heated  body ;  for,  while  the  cooling 
effects  of  the  air,  by  conduction,  is  the  same  on  all  substances, 
and  in  all  states  of  the  surface  of  those  substances,  radiation 
varies  very  materially,  according  to  the  nature  of  the  surface. 

The  influence  of  the  air,  by  its  power  of  conduction,  varies 
also  with  its  elasticity.  The  greater  its  elastic  force,  the  greater 
also  is  its  power  of  cooling,  according  to  the  following  law :  — 
When  the  elasticity  of  the  air  varies  in  a  geometrical  progres- 
sion whose  ratio  is  2,  its  cooling  power  also  changes  in  a  geo- 
metrical progression  whose  ratio  is  1.366. 

The  same  law  holds  with  all  gases,  as  well  as  with  atmos- 
pheric air  ;  but  the  ratio  of  the  progression  varies  with  each  gas. 

To  show  the  relative  velocities  of  cooling  at  different  temper- 
atures, the  following  table,  constructed  from  the  experiments  of 
Petit  and  Dulong,  is  given.  The  first  column  shows  the  excess 
of  temperature  of  the  heated  body  above  the  surrounding  air ; 
the  second  column  shows  the  rate  of  cooling  of  a  thermometer 
with  a  plain  bulb,  and  the  third  column  gives  the  rate  of  cooling 
when  the  bulb  was  covered  with  silver  leaf.  The  fourth  column 
shows  the  amount  due  to  the  cooling  of  the  air  alone ;  and  by 
deducting  this  from  the  second  and  third  columns  respectively, 


160 


PRINCIPLES  OF  HEATING  HOT-HOUSES. 


we  shall  find  what  is  the  amount  of  radiation  under  the  two 
different  states  of  surface,  noticed  at  the  top  of  the  second  and 
third  columns.  * 


Excess  of  temperature 
of  the  thermometer 
above  that  of  the  air. 
Centigrade  Scale. 

Total    velocity    of 
cooling  of  the  na- 
ked bulb. 

Total  velocity  of  cool- 
ing of  the  bulb  cov- 
ered with  silver  leaf. 

Amount  of  cooling  due 
to  conduction  of  air 
alone. 

260° 

24-42 

10-96 

8-10 

240° 

21-12 

9-82 

7-41 

220° 

17-92 

8-59 

6-61 

200° 

15-30 

7-57 

5-92 

180° 

13-04 

6-57 

5-19 

160° 

10-70 

5-59 

4-50 

140° 

8-75 

4-61 

3-73 

120° 

6-82 

3-80 

3-11 

100° 

5-57 

3-06 

2-53 

80° 

4-15 

2-32 

1-93 

60° 

2-86 

1-60 

1-33 

40° 

1-74 

•96 

•80 

20° 

•77 

•42 

•34 

10° 

•37 

•19 

•14 

Some  very  remarkable  effects  may  be  perceived  by  an  inspec- 
tion of  the  above  table.  It  appears  that  the  ratio  of  heat  lost  by 
contact  of  the  air  alone,  is  constant  at  all  temperatures  ;  that  is, 
whatever  is  the  ratio  between  40°  and  80°,  for  instance,  is  also 
the  ratio  between  80°  and  160°,  or  between  100°  and  200°. 
This  law  is  expressed  by  this  formula  : 


where  t  represents  the  excess  of  temperature,  and  n  a  number 
which  varies  with  the  size  of  the  heated  body.  In  the  case 
represented  in  the  foregoing  table,  n  =  0.00857. 

Another  remarkable  law,  is  that  the  cooling  effect  of  the  air  is 
the  same,  for  the  like  excess  of  heat,  on  all  bodies,  without 
regard  to  the  particular  state  or  nature  of  their  surface.  This 


*  The  temperatures  of  this  table  are  expressed  in  degrees  of  the  Cen- 
tigrade thermometer,  as  the  zero  of  this  thermometer  is  the  freezing 
point  of  water,  and  from  that  to  the  boiling  point  of  the  same  fluid  is 
100°.  In  order  to  find  the  number  of  degrees  on  Fahrenheit's  scale, 
which  answers  to  any  given  temperature  of  the  Centigrade,  multiply 
the  number  of  degrees  of  Centigrade  by  9,  and  divide  the  product  by  5  j 
add  32  to  the  quotient  thus  obtained,  and  this  sum  will  be  the  number 
of  degrees  of  Fahrenheit  required. 


PRINCIPLES  OTF  HEATING  HOT-HOUSES.  161 

was  ascertained  by  Petit  and  Dulong,  in  a  series  of  experiments, 
not  necessary  here  to  detail,  but  which  proved  the  accuracy  of 
the  deduction. 

By  comparing  the  second  and  third  columns  of  the  above 
table,  it  will  be  immediately  perceived  that  the  loss  of  heat  by 
radiation  varies  greatly,  with  the  nature  of  the  radiating  sur- 
face ;  though,  whatever  be  the  nature  of  the  surface,  the  loss  of 
heat  is  the  same  in  all  cases,  though  in  a  different  ratio. 

It  should  be  observed,  that,  in  this  table,  the  second,  third, 
and  fourth  columns  show  the  number  of  degrees  of  heat  which 
were  lost  per  minute  by  the  body  which  was  subject  to  the 
experiment ;  and,  therefore,  these  numbers  represent  the  velocity 
of  cooling. 

The  fact,  already  adverted  to,  that  the  ratio  of  cooling  in 
those  bodies  that  radiate  least  is  more  rapid  at  low  tempera- 
tures, and  less  at  high  temperatures,  than  those  bodies  that 
radiate  most,  is,  perhaps,  one  of  the  most  remarkable  of  the  laws 
of  cooling.  It  was  first  deduced  experimentally  by  Petit  and 
Dulong,  arid  it  may  be  mathematically  proved  from  their  for- 
mula ;  but  it  is  unnecessary  here  to  enter  into  the  investigation. 
It  appears,  however,  that  when  the  total  cooling  of  two  bodies  is 
compared,  the  law  is  more  rapid  at  low  temperatures  for  the 
body  which  radiates  least,  and  less  rapid  for  the  same  body  at 
high  temperatures ;  though  separately,  for  conduction  and  radia- 
tion, the  law  of  cooling  is,  for  the  former,  irrespective  of  the 
nature  of  the  body,  and  for  the  latter,  that  all  bodies  preserve  at 
every  difference  of  temperature  a  constant  ratio  in  their  radi- 
ating power. 

It  is  not  our  purpose  to  enter  minutely  into  detail  on  the  laws 
of  heat,  which  will  be  found  in  modern  works  on  chemistry, 
and  which  ought  to  form  part  of  the  studies  of  all  young  gar- 
deners who  wish  to  become  acquainted  with  the  principles  of 
hot-house  management.  We  will  now  proceed  to  consider  the 
specific  properties  of  air  and  water  as  agents  in  the  heating  of 
horticultural  structures. 

3.  Specific  heat  of  air  and  water.  —  Very  erroneous  notions 
are  entertained  by  many  persons  as  to  the  absolute  quantity  of 


162  PRINCIPLES  OF  HEATING  HOT-HOUSES. 

heat  taken  up  by  different  substances.  To  ascertain,  therefore, 
the  effect  a  certain  quantity  of  water  will  produce  in  warming 
the  air  of  a  hot-house,  there  appears  to  be  no  better  method 
than  that  of  computing  from  the  specific  heat  of  gases  compared 
with  water. 

Every  substance  has  its  peculiar  specific  heat.  Now,  one 
cubic  foot  of  water,  by  losing  one  degree  of  heat,  will  raise  the 
temperature  of  2990  cubic  feet  of  air  the  extent  of  one  degree ; 
and,  by  the  same  rule,  by  losing  10°  of  its  heat,  it  will  raise  the 
temperature  of  2990  cubic  feet  of  air  10  degrees;  and  so  with 
similar  quantities  in  similar  proportions. 

In  order  to  know  the  time  it  will  take  to  heat  a  certain  quan- 
tity of  air  any  required  number  of  degrees,  by  means  of  hot 
water  contained  in  metal  pipes,  we  must  calculate  the  effect 
from  direct  experiment ;  and,  as  the  radiating  and  conducting 
powers  of  different  substances  differ  considerably,  it  is  necessary 
that  the  experiment  be  made  with  the  same  material  as  the 
pipes  for  which  we  wish  to  estimate  the  effect. 

From  data  obtained  by  experiments  on  the  cooling  of  iron 
pipes,  it  appears  that  the  water  contained  in  a  pipe  4  inches  in 
diameter  loses  -851  of  a  degree  of  heat  per  minute,  when  the 
excess  of  its  temperature  is  above  125  degrees  above  that  of  the 
surrounding  air.  There  one  foot  in  length  of  a  pipe  4  inches 
diameter  will  heat  222  cubic  feet  of  air  one  degree  per  minute, 
when  the  difference  between  the  temperature  of  pipe  and  the 
air  is  125  degrees. 

To  calculate  from  this  data,  however,  the  length  of  a  pipe,  of 
any  given  size,  that  will  be  necessary  to  warm  a  house,  and  to 
maintain  it  at  any  given  temperature  under  a  certain  external 
temperature,  it  will  be  necessary  to  estimate  the  heat  lost  by 
the  conducting  and  radiating  power  of  the  glass,  and  of  any 
metallic  substance  used  in  the  structure. 

Heating  horticultural  structures  is  a  very  different  matter 
from  heating  solid  opaque  buildings ;  and  here  many  erectors 
of  heating  apparatus  fall  into  error.  They  suppose,  because  an 
apparatus  of  certain  power  heated  a  large  building,  —  a  church 
or  a  hall,  —  one  of  proportionate  dimensions  should  warm  a  hot- 
house of  proportionate  size,  without  taking  into  full  considera- 


PRINCIPLES    OF    HEATING    HOT-HOUSES.  163 

tion  the  great  difference  of  the  external  radiation,  and  the  con- 
duction of  heat  by  the  materials  of  the  building. 

The  loss  of  heat  by  buildings  covered  with  glass  is  very  great. 
It  appears,  by  experiment,  that  one  square  foot  of  glass  will  cool 
down  1-279  cubic  feet  of  air  as  many  degrees  per  minute  as  the 
internal  temperature  of  the  house  exceeds  the  temperature  of 
the  external  air;  thus,  if  the  difference  between  the  external 
temperature  and  the  temperature  of  the  house  be  30  degrees, 
then  1-279  cubic  feet  of  air  will  be  cooled  30  degrees  by  each 
square  foot  of  glass ;  or,  more  correctly,  as  much  heat  as  is  equal 
to  this  will  be  given  off  by  each  square  foot  of  glass,  for,  in  real- 
ity, a  very  much  larger  quantity  of  air  will  be  affected  by  the 
glass,  but  it  will  be  cooled  to  a  less  extent.  The  real  loss  of 
heat,  however,  from  the  house  will  be  what  is  here  stated. 

There  are  various  causes  likely  to  affect  these  calculations, 
such  as,  — 

High  winds,  which  are  found  to  reduce  the  internal  tempera- 
ture more  than  actual  cold,  or  even  frost ; 

Condensation  of  moisture  on  the  glass,  which  prevents  the 
escape  of  heated  air ;  and,  when  a  certain  temperature  is  main- 
tained within,  prevents  radiation  from  the  glass  to  a  great 
degree ; 

The  extent  of  wood  in  the  roof  of  the  house,  which  also  pre- 
vents radiation  and  conduction,  as  in  the  case  of  metallic  roofs. 

These  circumstances  will  be  found  to  affect,  in  a  greater  or 
less  degree,  the  air  of  the  house,  though,  under  general  circum- 
stances, these  calculations  will  be  nearly  correct. 

In  estimating  the  quantity  of  glass  surface  contained  in  a 
building,  the  extent  of  wood  surface  must  be  carefully  excluded. 
This  is  particularly  necessary  in  all  horticultural  buildings, 
where  the  maximum  of  heating  power  is  dependent  upon  the 
estimate  taken.  The  readiest  way  of  calculating,  and  suffi- 
ciently accurate  for  ordinary  purposes,  is  to  take  the  square  sur- 
faces of  the  sashes,  and  then  deduct  one  eighth  of  the  amount  for 
wood  work.  In  the  generality  of  horticultural  buildings,  the 
wood  work  fully  amounts  to  this  quantity.  When  the  frames 
and  sashes  are  made  of  metal,  the  radiation  of  heat  will  be  quite 


164 


PRINCIPLES    OF    HEATING    HOT-HOUSES. 


as  much  from  the  frame  as  from  the  glass ;  therefore  no  deduc- 
tion is  required  in  such  cases. 

From  the  preceding  calculations  the  following  corollary  may 
be  drawn :  — 

The  quantity  of  air  to  .be  warmed  per  minute  in  habitable 
rooms  and  public  buildings,  must  be  3^  cubic  feet  for  each 
person  the  room  contains,  and  l£  cubic  feet  for  each  square 
foot  of  glass. 

For  conservatories,  forcing-houses,  and  all  buildings  of  this 
description,  the  quantity  of  air  warmed  per  minute  must  be  l£ 
cubic  feet  for  each  square  foot  of  glass  the  structure  contains. 

When  the  quantity  of  air  required  to  be  heated  has  thus  been 
ascertained,  the  length  of  pipe  to  heat  it  by  hot  water  may  be 
found  by  the  following  table  : 

Table  of  the  quantity  of  pipe  4  inches  diameter  which  will  heat  1000  cubic 
feet  of  air  per  minute,  any  required  number  of  degrees.  The  temperature 
of  the  pipe  being  200°  Fahrenheit :  — 


Temperature  of  exter- 
nal air. 

Temperature  at  which  the  house  is  required  to  be  kept. 

Fahrenheit's  scale.  |  45°  |  50J  |  55°  60J  |  65°  |  70°  |  75° 

80J  |  85°  |  90° 

10° 

126 

150 

174 

200 

229 

259  ;  292 

328 

367 

409 

12° 

119 

142 

166 

192 

220 

251  283 

318 

357 

399 

14° 

112 

135 

159 

184 

212 

242 

274 

309 

347 

388 

16° 

105 

127 

151 

176 

204 

233 

265 

300 

337 

378 

18° 

98 

120 

143 

168 

195 

225 

256 

290 

328 

368 

20° 

91 

112 

135 

160 

187 

216 

247 

281 

318 

358 

22° 

83 

105 

128 

152 

179 

207 

238 

271 

308 

347 

24° 

76 

97 

120 

144 

170 

199  '  229 

262 

298 

337 

26° 

69 

90 

112 

136 

162 

190 

220 

253 

288 

327 

28° 

61 

82 

104 

128 

154 

181 

211 

243 

279 

317 

30° 

54 

75 

97 

120 

145 

173 

202 

234 

269 

307 

Freezing  point  32° 

47 

67 

89 

112 

137 

164 

193 

225 

259 

296 

34° 

40 

60 

81 

104 

129 

155  184 

215  219 

286 

36° 

32 

52 

73 

96 

120 

149 

175 

206 

239 

276 

38° 

25 

45 

66 

88 

112 

138 

166 

196 

229 

266 

40° 

18 

37 

58 

80 

104 

129 

157 

187 

220 

255 

42° 

10 

30 

50 

72 

97 

121 

148 

178 

210 

245! 

44° 

3 

22 

42 

64 

85 

112 

139 

168 

200 

235 

46° 

15 

34 

56 

79 

103 

130 

159 

190 

225 

48° 

7 

27 

48 

70 

95 

121 

150 

181 

215 

50° 

19 

40 

62 

86 

112 

140 

171 

204 

52° 

11 

32 

54 

77 

103 

131 

161 

193 

To  ascertain,  by  the  above  table,  the  quantity  of  pipe  required 
to  heat  1000  cubic  feet  of  air  per  minute,  find,  in  the  first  column, 


PRINCIPLES    OF    HEATING   HOT-HOUSES. 


165 


the  temperature  which  corresponds  to  that  of  the  external  air, 
which  may  be  the  medium  (or  average)  of  your  locality. 
Then,  in  the  other  column,  find  the  temperature  required  in  the 
house ;  then,  in  this  latter  column,  and  on  the  line  which  cor- 
responds with  the  external  temperature,  the  required  number  of 
feet  of  pipe  will  be  found. 

Supposing,  now,  that  a  forcing-house  is  to  be  kept  at  75  de- 
grees, and  the  average  of  the  external  thermometer  in  the 
coldest  weather,  taken  at  10°  (Fah.)  ;  then,  by  the  foregoing 
table,  we  find,  under  the  column  75°,  and  on  the  line  10°,  for 
external  temperature,  the  quantity  292,  which  is  the  number  of 
feet  of  pipe  required  to  heat  1000  cubic  feet  of  air  per  minute, 
the  proposed  number  of  degrees.  Of  course,  the  volume  of  air 
in  the  house  must  be  previously  ascertained.  Any  other  differ- 
ence of  temperature  may  be  found  in  the  same  way. 

It  will  thus  be  perceived,  that  the  amount  of  heat  required 
for  warming  a  glazed  structure  is  much  greater  than  that  re- 
quired for  warming  an  opaque  building  of  the  same  size,  in 
consequence  of  the  radiation  of  heat  from  its  surface ;  and  the 
difference  is  much  greater  than  the  allowance  made  by  erectors 
of  heating  apparatuses,  under  general  circumstances. 

To  ascertain  the  effect  of  glass  windows  in  cooling  the  atmos- 
phere of  a  house,  the  following  experiments  were  made,  with  a 
vessel  as  nearly  as  possible  the  same  thickness  as  the  glass 
ordinarily  used  for  glazing.  The  temperature  of  the  house,  in 
these  experiments,  was  65°  ;  the  thickness  of  the  glass  was  .0825 
of  an  inch ;  the  surface  of  the  vessel  measured  34-296  square 
inches,  and  it  contained  9-794  cubic  inches  of  water.  The  time 
in  which  this  vessel  cooled,  when  filled  with  hot  water,  is  shown 
as  follows :  — 


Thermometer 
cooled. 

Observed 
time  of 
cooling. 

Calculated 
time    of 
cooling. 

Average  rate  of  the 
observed  time  of 
cooling. 

from          |          to 

150° 
150 
150 
150 

140° 
130 
120 
110 

6'  40" 
14  50 
23  30 
34     0 

&  51" 
14  43 
23  40 
34     0 

1-176°  per  minute, 
at  an  excess  of  65° 
above  the   tempera- 
ture of  the  air. 

From  the  average  rate  of  cooling  here  given,  the  effect  of 
glass  in  cooling  the  atmosphere  of  a  room  may  easily  be  calcu- 


166  PRINCIPLES    OF    HEATING   HOT-HOUSES. 

lated,  as  the  specific  heat  of  equal  volumes  of  air  and  water  is 
as  1  to  2990.  The  above  average  will  show  that  each  square 
foot  of  glass  will  cool  1-279  cubic  feet  of  air  one  degree  per 
minute,  when  the  temperature  of  the  glass  is  one  degree  above 
that  of  the  external  air. 

But  by  this  we  can  only  find  the  effect  of  glass  in  a  still  at- 
mosphere, and,  therefore,  to  find  the  effect  of  glass  in  cooling 
the  volume  of  a  hot-house,  especially  when  exposed  to  the  action 
of  winds,  further  experiments  are  necessary,  of  which  we  shall 
treat  in  a  subsequent  part  of  this  work,  in  connection  with  "  pro- 
tection of  hot-house  roofs  during  the  night." 


, 


SECTION    III. 

HEATING     BY     HOT     WATER,     HOT     AIR,     AND     STEAM. 

1.  THE  practice  of  employing  hot  water,  circulating  through 
metallic  tubes,  or  wooden  troughs,  for  diffusing  artificial  heat  in 
horticultural  structures,  though  of  recent  origin,  has  now  become 
so  general,  that  its  merits  are  fully  acknowledged  as  the  best 
method  that  has  yet  been  invented,  to  effect  the  purpose  with 
efficiency  and  economy.  Until  the  last  few  years,  —  although 
its  powers  and  properties  were  fully  known,  —  it  had  been 
chiefly  confined  to  a  few  cases  of  experiment,  rather  than  to  any 
general  or  useful  purpose. 

The  present  day,  however,  has  fully  revealed  its  merits,  and 
shown  the  great,  the  unlimited,  extent  of  its  practical  application 
and  general  utility.  When  we  see  such  an  immense  structure 
as  the  great  Palm  house,  lately  erected  at  Kew  Gardens,  in 
London,  heated  with  hot  water  in  preference  to  all  other  modes ; 
when  we  see  the  lately  applauded  mode  of  heating  by  steam 
abandoned;  when  we  see  the  powerful,  but  unsuccessful,  at- 
tempt to  establish  a  new  system  of  heating  by  hot  air,  called 
Polmaise,  by  some  of  the  first  horticulturists  of  England ;  when 
we  see  this  system,  notwithstanding  its  powerful  supporters, 
driven  into  obscurity,  and  all  but  annihilated,  by  the  well-tried 
superiority  of  hot  water,  which  maintains  its  proud  preeminence 
over  all  other  methods  of  heating,  and  has  its  superiority  ac- 
knowledged, even  by  its  enemies. 

One  of  the  greatest  advantages  which  this  mode  of  heating 
possesses  over  all  others,  is,  that  a  greater  permanency  of  tem- 
perature can  be  obtained  by  it,  than  by  any  other  method.  The 
difference  between  an  apparatus  heated  by  hot  water,  and  one 
heated  by  steam,  is  not  less  remarkable,  in  this  particular,  than 
in  its  superior  economy  of  fuel. 
15 


168  HEATING    BY    HOT   WATER,   HOT   AIR,  AND    STEAM. 

2.  Comparison  of  heat  in  water  and  steam.  —  The  heating  of 
horticultural  buildings  by  steam  had  its  day  and  its  admirers, 
though  both  are  now  numbered  among  the  things  that  were. 
Even  if  the  original  outlay  were  equal,  the  additional  outlay  for 
fuel,  the  risk  of  explosion  from  neglect,  and  the  want  of  perma- 
nency in  the  apparatus  to  maintain  the  heat  for  any  length  of 
time,  are  insuperable  objections  to  its  adoption.  Among  many 
instances  that  could  be  given  of  this  method  of  warming  large 
houses,  we  might  mention  the  large  Palm  house,  in  the  Royal 
Botanic  Garden  of  Edinburgh,  which  was  erected  when  heating 
by  steam  was  in  the  height  of  its  fame.  This  house  is  about 
fifty  feet  high  and  seventy-five  feet  wide,  in  the  form  of  an 
octagon ;  the  pipes  are  laid  around  the  side  of  the  wall.  There 
is  a  contrivance,  however,  resorted  to  here,  in  connection  with 
the  system,  to  which  its  success  in  heating  the  house  may  be 
somewhat,  if  not  entirely,  attributed.  The  steam  is  thrown  into 
large  iron  boxes,  loosely  filled  with  stones  and  pieces  of  brick, 
for  the  retention  and  absorption  of  the  heat.  These  iron  boxes 
are  placed  underneath  the  shelf  that  surrounds  the  house,  and 
close  by  the  side  of  the  wall,  and  at  regular  distances  from 
each  other.  By  this  contrivance,  the  temperature  .of  the  house 
is  kept  up  for  a  considerable  time  longer  than  would  be  by  the 
circulation  of  the  steam  alone.  Indeed,  we  believe  it  was  found 
perfectly  impracticable  to  maintain  the  proper  temperature,  dur- 
ing cold  nights,  until  this  expedient  was  adopted,  viz.,  of  filling 
the  boxes  with  absorbing  materials. 

We  have  known  conservatories,  in  which  steam  apparatuses 
had  been  erected,  taken  down,  and  their  place  supplied  with 
others  of  hot  water,  merely  in  consideration  of  the  consumption 
of  fuel  and  extra  attention  required  by  a  steam  apparatus,  keep- 
ing the  danger  of  explosion  out  of  the  question. 

It  seldom  happens  that  the  pipes  of  a  hot-water  apparatus  can 
be  raised  to  so  high  a  temperature  as  212° ;  in  fact,  it  is  not 
desirable  to  do  so,  because  it  is  unnecessary  to  generate  steam, 
which  would  only  escape  by  the  air  vent,  without  affording  any 
available  heat.  Steam  pipes,  on  the  contrary,  must  always  be 
above  the  temperature  of  212°,  otherwise  steam  will  not  be  gen- 
erated ;  and  here  the  grand  point  to  be  attended  to  in  artificial 


HEATING    BY    HOT   WATER,    HOT    AIR,  AND    STEAM.  169 

heating  is  nullified,  namely,  the  diffusion  of  heat  at  a  low  tem- 
perature. A  given  length  of  steam  pipe,  however,  will  afford 
more  heat  than  one  heated  by  hot  water,  by  the  aggregate  cal- 
culation of  its  specific  heat.  But,  if  w«  consider  the  relative 
permanency  of  temperature,  we  shall  find  a  very  remarkable  dif- 
ference in  favor  of  pipes  heated  by  hot  water ;  and  the  calculations 
here  given  are  fully  confirmed  by  experience  and  observation. 

The  weight  of  steam,  at  the  temperature  of  212°,  compared 
with  the  weight  of  water  at  212°,  is  about  as  1  to  1694,  so  that 
a  tube  that  is  filled  with  water  at  212°  contains  1694  times  as 
much  matter  as  one  of  equal  size  filled  with  steam.  If  the 
source  of  heat  be  withdrawn  from  the  steam  pipes,  the  temper- 
ature will  soon  fall  below  212°,  and  the  steam  immediately 
in  contact  with  the  pipes  will  condense ;  but,  in  condensing, 
the  steam  parts  with  its  latent  heat,  and  this  heat,  in  passing 
from  the  latent  to  the  sensible  state,  will  again  raise  the  tem- 
perature of  the  pipes ;  but,  by  the  withdrawal  of  the  heat  from 
the  boiler,  the  action  of  the  cold  air  on  the  pipes  quickly  con- 
denses the  whole  of  the  steam  contained  in  them,  which,  when 
condensed,  possesses  just  as  much  heating  power  as  the  same 
bulk  of  water  at  a  similar  temperature.  This  water  now  occu- 
pies only  T^g-¥  Part  °f  t^le  sPace  which  the  steam  originally  did 
in  the  pipes. 

The  specific  heat  of  uncondensed  steam,  compared  with  water, 
is,  for  equal  weights,  as  -8470  to  1 ;  but  the  latent  heat  of 
steam  being  estimated  at  1000  degrees,  we  shall  find  the  relative 
heat  obtainable  from  equal  weights  of  condensed  steam  and  of 
water,  reducing  both  from  the  temperature  of  212°  to  60°,  to  be 
as  7-425  to  1 ;  but  for  equal  bulks  it  would  be  as  1  to  228 ;  that 
is,  bulk  for  bulk,  water  will  give  out  228  times  as  much  heat  as 
steam,  reducing  both  to  the  temperature  of  60°.  A  given  bulk 
of  steam,  therefore,  will  lose  as  much  of  its  heat  in  one  minute, 
as  the  same  bulk  of  water  will  lose  in  three  hours  and  three 
quarters. 

It  must  be  considered,  however,  that  when  the  water  and 
steam  are  both  circulated  in  iron  pipes,  the  rate  of  cooling  will 
be  somewhat  different  from  this  ratio,  in  consequence  of  the 


170  HEATING   BY    HOT    WATER,   HOT   AIR,  AND    STEAM. 

much  larger  quantity  of  heat  contained  in  the  metal,  than  in  the 
steam  with  which  the  pipe  is  filled. 

The  specific  heat  of  cast  iron  being  nearly  the  same  as  water, 
the  water  being  1000  and  the  iron  1100,  if  we  take  two  similar 
pipes,  four  inches  in  diameter  and  one  fourth  of  an  inch  thick, 
the  one  filled  with  water  and  the  other  with  steam,  each  at  the 
temperature  of  212°,  the  one  which  is  filled  with  water  contains 
4-68  times  as  much  heat  as  the  one  which  is  filled  with  steam. 
Therefore,  if  the  pipe  with  the  steam  cools  down  to  the  temper- 
ature of  60°  in  one  hour,  the  one  filled  with  water  would  require 
four  hours  and  a  half,  under  the  same  circumstances,  before  it 
reached  the  like  temperature. 

But  this  is  merely  reckoning  the  effect  of  the  pipe  and  the 
fluid  contained  in  it.  In  a  steam  apparatus,  this  is  all  that  is 
effective  in  giving  out  heat ;  but  in  a  hot-water  apparatus  there 
is  likewise  the  heat  from  the  water  contained  in  the  boiler,  and 
even  of  the  brick-work  around  the  boiler,  all  which  tends  to 
increase  the  heat  of  the  pipes,  long  after  the  fire  is  extinguished. 
In  the  one,  the  heat  will  continue  to  circulate  through  the  pipes 
as  long  as  any  heat  remains  about  the  fire-place,  because  the 
circulation  will  continue  in  the  pipes  until  the  whole  apparatus 
is  cooled  down.  But,  in  the  case  of  steam  pipes,  as  soon  as  the 
water  in  the  boiler  falls  below  the  boiling  point,  (212°,)  circula- 
tion ceases,  and  the  pipes  then  begin  to  cool,  the  remaining  heat 
in  the  boiler  and  furnace  goes  for  nought. 

From  these  causes  the  difference  in  permanency  of  hot  water 
and  steam  will  be  clearly  apparent,  and  the  fact  of  a  house 
heated  with  hot  water  keeping  up  its  temperature  at  least  six 
times  as  long  as  one  heated  with  steam,  will  be  fully  understood 
by  those  interested  in  the  matter.  These  considerations  are  of 
the  utmost  importance  to  those  erecting  horticultural  build- 
ings, or,  indeed,  any  other  kind  of  buildings  requiring  artificial 
heat.  This  admirable  property,  which  water  possesses,  of  re- 
taining its  heat,  of  carrying  it  to  any  distance,  and,  without 
difficulty,  giving  it  out  gradually,  or  retaining  it  for  many  hours, 
renders  it  of  vast  importance  to  gardeners,  and  prevents  the 
necessity  of  that  constant  attention  to  the  fire,  which  forms  so 
serious  an  objection  in  all  other  methods  of  heating. 


HEATING    BY    HOT    WATER,    HOT    AIR,  AND    STEAM.  171 

We  find,  by  experience,  that  no  system  of  heating  horticul- 
tural buildings  in  all  respects  answers  the  purpose  so  well  as  a 
hot-water  apparatus,  well  constructed,  and  judiciously  arranged, 
in  regard  to  the  amount  of  work  it  has  to  do,  so  that  it  may  not 
be  necessary  to  strain  it,  on  exigencies,  to  its  maximum  point  of 
strength.  In  whatever  point  of  view  it  may  be  regarded,  it  is, 
undoubtedly,  the  best  for  all  practical  purposes  ;  and  the  best 
possible  evidence  of  its  utility  is  derived  from  the  fact,  that  no 
case  has  ever  come  under  our  knowledge,  wherein  it  has  failed 
to  give  complete  satisfaction,  when  it  has  been  properly  con- 
structed, rightly  managed,  and  judiciously  arranged,  in  regard 
to  supplying  a  sufficient  amount  of  radiating  surface  for  the 
work  it  has  to  do. 

3.  Comparison  of  hot  air  with  hot  water,  as  a  mode  of  heating 
horticultural  structures.  —  Various  erroneous  opinions  and  prin- 
ciples have  been  theoretically  and  practically  promulgated,  in 
regard  to  hot-air  heating ;  and,  carrying  with  them,  in  general, 
some  degree  of  plausibility,  and  in  some  cases  emanating  from 
men  of  learning,  have  led  many,  who  have  not  studied  the  mat- 
ter attentively,  into  very  great  errors.  However  invidious, 
therefore,  may  be  the  task  of  pointing  out  such  errors,  we  con- 
sider it  our  duty,  when  treating  on  the  subject  at  large,  not  only 
to  exhibit  what  we  consider  to  be  the  true  principles,  but  to 
show  where  erroneous  principles  have  been  adopted.  This  must 
serve  as  an  apology  for  the  freedom  with  which  the  advocates 
of  Polmaise,  and  other  methods  of  hot-air  heating,  and  the  sys- 
tems they  approve,  are  descanted  on  in  this  section. 

We  have  already  observed  that  the  cooling  of  a  heated  body, 
under  ordinary  circumstances,  is  evidently  the  combined  effect 
of  radiation  and  conduction.  The  conductive  power  of  the  air 
is  principally  owing  to  the  mobility  of  its  particles,  for,  otherwise, 
it  is  one  of  the  worst  conductors  we  are  acquainted  with. 

Atmospheric  air,  in  passing  into  a  house  over  a  highly  heated 
surface,  must  necessarily  lose  a  large  quantity  of  its  contained 
moisture ;  [see  1.  Effects  of  Artificial  Heat,  of  the  preceding 
section ;]  and,  as  its  capacity  for  taking  up  moisture  is  increased 
according  to  its  temperature,  it  follows  that  a  great  demand 
15* 


172  HEATING   BY   HOT   WATER,   HOT   AIR,  AND   STEAM. 

must  be  made  upon  the  moisture  of  the  house,  upon  the  plants, 
and  upon  everything  else  within  its  influence  capable  of  giving 
off  moisture.  This  is  also  the  case  with  hot-water  pipes.  But 
here  the  advantage  of  the  latter  is  plainly  illustrated ;  for  while 
a  hot-air  stove  abstracts  the  moisture,  in  excess,  from  that  part 
of  the  house  nearest  to  the  aperture  of  ingress,  hot-water  pipes 
radiate  the  heat  at  a  low  temperature  equally  over  the  whole 
surface,  and,  as  the  temperature  at  which  the  heat  is  radiated  is 
comparatively  low,  little  or  no  moisture  is  abstracted.  Some 
suppose  that  they  get  a  fine  moist  heat  from  hot-water  pipes. 
This,  however  sound  and  sensible  it  may  appear,  is,  nevertheless, 
a  practical  fallacy,  the  fact  of  the  case  being  this,  —  that,  instead 
of  the  moisture  of  the  house  being  taken  up  by  the  air,  as  in 
the  case  of  Polmaise,  and  other  stoves,  the  warm  air  of  the 
pipes  being  so  much  lower  in  temperature  than  that  of  the 
stoves,  it  cannot  take  it  up,  and  hence  the  moisture  remains 
with  the  plants  and  the  atmosphere  in  its  original  purity.  In 
fact,  there  is  no  difference  between  the  heat  radiated  from  stone, 
brick,  or  iron,  unless  it  be  mixed  with  extraneous  gases,  by  heat- 
ing these  bodies  to  a  high  temperature. 

To  supply  the  moisture  required  by  the  heated  air,  water  may 
be  placed  in  evaporating  pans,  in  connexion  with  the  current 
of  ingress;  but,  as  we  have  already  shown,  though  moisture 
may  be  supplied,  the  hydrogen  of  the  rarefied  air  still  remains 
uncombined,  and,  until  the  air  be  replaced  by  a  fresh  volume 
from  the  external  atmosphere,  its  impurities  still  remain. 

With  regard  to  the  motion  and  circulation  of  the  atmosphere 
of  a  hot-house,  the  system  of  heating  by  hot  air  possesses,  the- 
oretically, some  advantages  over  all  others.  Strictly  speaking, 
however,  this  has  scarcely  a  practical  foundation.  If  hot  air  be 
admitted  in  currents,  the  atmosphere  will  be  agitated,  certainly, 
but  the  house  will  be  very  unequally  heated,  as  the  heated  air 
will  pass  upward  in  currents,  at  the  aperture  of  its  entrance, 
without  diffusing  itself  over  the  lower  surface  of  the  house. 
Air  expands,  when  heated,  ^^  of  its  bulk  for  each  degree  of 
Fahrenheit,  and  the  velocity  of  its  motion  is  equal  to  the  addi- 
tional height  which  a  given  weight  of  heated  air  must  have,  in 
order  to  balance  the  same  weight  of  cold  air ;  and  as  all  rare 


HEATING   BY   HOT   WATER,  HOT   Affi,  AND   STEAM.  173 

bodies  tend  to  rise  vertically,  in  a  dense  medium,  it  follows,  that 
when  heated  air  enters  a  house  by  an  aperture  at  one  part  of  it, 
a  very  large  portion  of  the  heated  air  thus  entering,  must  rise 
immediately  towards  the  roof;  and  in  practice  we  find  this  to  be 
exactly  the  case.  For,  let  any  person  examine  the  roof  of 
a  hot-house  in  a  frosty  night,  heated  by  a  hot-air  stove,  and  he* 
will  perceive  the  part  immediately  above  the  entrance  of  the 
air  quite  warm  by  the  ascending  heat,  while  all  the  rest  of  the 
roof  may  be  covered  with  ice  or  snow. 

But  the  atmosphere  of  a  house  heated  artifically,  by  whatever 
means,  is  always  in  motion ;  with  hot-water  pipes  it  may  be 
less  perceptible,  for  the  reasons  already  stated,  but  it  is  not 
the  less  real.  The  motion  given  to  the  atmosphere  of  a  house 
depends  upon  the  difference  of  temperature  between  the  two 
bodies  of  air,  externally  and  internally ;  therefore  a  motion  must 
continue  in  the  air  of  a  house  artificially  warmed,  so  long  as  the 
house  requires  warming,  —  that  is,  as  long  as  any  difference  ex- 
ists between  the  internal  and  external  atmospheres. 

Some  advocates  of  hot-air  heating  found  their  arguments  upon 
the  fact  that  air  can  be  raised  to  a  higher  temperature,  in  a 
given  time,  by  a  given  amount  of  caloric,  than  water.  This  is 
probably  true,  if  we  calculate  according  to  the  bulk,  without  re- 
gard to  the  density,  of  the  respective  bodies  ;  but,  supposing  it  to 
be  true,  then  we  know  that,  by  the  law  already  referred  to,  its 
rapidity  in  warming  will  just  be  in  exact  proportion  to  its  rapid- 
ity in  cooling,  and  vice  versa.  It  is,  therefore,  manifest,  that  this 
property  militates  against  it  as  an  agent  in  heating  horticultural 
buildings,  as  it  is  well  known  to  be  an  all-important  point,  in 
warming  these  structures,  to  obtain  an  equilibrium  of  heat  for 
the  greatest  length  of  time,  and  with  the  least  possible  amount 
of  attention,  and  experience  has  fully  concluded  that  this  is  most 
effectually  and  most  easily  obtained  by  the  circulation  of  hot 
water  through  wooden  and  metallic  radiators  and  conductors. 

Suppose,  for  instance,  that  a  house,  containing  4000  cubic 
feet  of  air,  is  required  to  be  heated,  from  32°  to  60°,  and 
suppose  the  external  thermometer  to  remain  stationary  at  this 
point ;  then,  by  calculation,  we  find  that  it  requires  double  the 
amount  of  fuel  to  heat  the  atmosphere  through  the  28  degrees 


174  HEATING   BY    HOT   WATER,   HOT   AIR,   AND    STEAM. 

between  these  two  points,  by  means  of  water,  that  it  does 
through  the  medium  of  air,  i.  e.,  by  direct  communication,  in 
each  case  the  calorific  action  being  in  pretty  exact  ratio  to  the 
combustion,  and  both  acting  under  the  most  favorable  circum- 
stances. This  would,  at  first  view,  decide  us  in  favor  of  hot 
air  as  a  means  of  heating,  in  preference  to  hot  water ;  and  the 
fact  that  the  heat  becomes  more  rapidly  sensible  by  hot  air,  has 
induced  many  to  come  to  a  premature  conclusion  on  this  point. 

Let  us,  however,  take  another  view  of  the  position  here 
alluded  to,  and  consider  the  two  methods  in  regard  to  their  per- 
manency of  heating  power.  We  find  also,  by  calculation,  that 
while  the  temperature  of  the  house  is  maintained  at  60°  for 
3*25  hours  by  hot  air,  with  the  same  amount  of  combustion  the 
temperature  of  60°  is  maintained  for  10  hours  by  hot  water,  or 
three  times  the  period  that  the  equilibrium  is  maintained  by  hot 
air.  The  same  experiment  shows  that  2  bushels  of  coal  will 
warm  an  equal  volume  of  air  in  a  hot-house  the  same  length  of 
time  that  5-067  bushels  will  warm  by  direct  connexion  of  its 
particles  with  the  source  of  heat. 

Now,  in  a  large  house,  or  number  of  houses,  this  saving  of 
fuel  would,  in  a  few  years,  amount  to  the  difference  of  cost  be- 
tween the  two  apparatuses,  keeping  out  of  the  question  the  saving 
of  labor,  the  cleanliness  and  neatness  of  the  one  compared  with 
the  other.  In  regard  to  these  numbers,  we  may  remark,  that 
the  calculations  of  some  experienced  and  intelligent  gardeners, 
drawn  from  accurate  observation,  have  made  the  difference  be- 
tween the  two  methods  still  greater,  in  regard  to  the  consump- 
tion of  fuel,  —  placing  this  position  in  still  stronger  light  than  by 
the  calculation  here  given. 

This  remarkable  difference  in  the  retention  of  heat  is  owing 
to  the  following  causes. 

First.  The  power  possessed  by  the  water  [as  already  ex- 
plained, see  "  Comparison  of  Water  and  Steam  "]  of  absorbing 
and  retaining  a  large  amount  of  heat,  and  giving  it  off  gradually, 
as  the  atmosphere  requires  it. 

Secondly.  Owing  to  the  body  of  metal  with  which  the  water 
is  surrounded,  which  also  absorbs  and  retains  a  large  amount 


HEATING    BY    HOT    WATER,   HOT    AIR,  AND   STEAM.  175 

of  heat,  and  parts  with  it  slowly  to  the  air  by  which  it  is  sur- 
rounded. 

Water  is  a  better  conductor  of  heat  than  air.  Every  gardener 
well  knows  how  rapidly  a  wet  mat,  or  any  other  wet  substance, 
will  carry  off  the  heat  in  a  frosty  night,  if  laid  over  a  hot-bed, 
or  green-house.  In  fact,  the  temperature  of  a  frame  under  such 
covering  will  fall  quicker  than  if  fully  exposed.  Yet  the  case 
is  different  if  the  mat  be  dry,  because  the  apertures  of  the  mat, 
and  also  the  space  between  it  and  the  glass,  are  filled  with  air 
at  rest,  —  because  the  latter  is  a  bad  conductor  of  heat,  and  the 
former  a  good  conductor.  In  a  tank  of  water  in  a  hot-house, 
the  thermometer  will  indicate  a  temperature  probably  10°  above 
the  atmosphere,  while,  by  plunging  the  hand  in  the  water,  it  will 
feel  about  10°  lower.  This  arises  from  the  power  possessed  by 
the  water  of  conducting  the  heat  from  the  hand  immersed  in  it. 
The  effect  in  all  these  cases  may  appear  different,  but  the  prin- 
ciple of  action  is  the  same.  Water  conducts  heat  rapidly  from 
a  body  warmer  than  itself,  and  conveys  it  to  a  colder  one. 

Let  a  stream  of  air  be  forced  through  a  tube  100  feet  in 
length,  entering  at  the  temperature  of  150°;  by  the  time  it  has 
travelled,  by  its  own  specific  gravity,  to  the  end  of  the  tube, 
it  will  be  reduced  to  the  temperature  of  the  external  atmosphere. 
A  stream  of  water,  under  the  same  circumstances,  will  travel  to 
the  end  of  the  tube  with  a  very  slight  diminution  of  its  tem- 
perature, probably  only  a  few  degrees,  and  will  have  heated  the 
tube,  if  a  good  conductor,  to  nearly  the  same  temperature  as 
itself  during  its  passage. 


SECTION    IV. 

HOT-WATER    BOILERS    AND    PIPES. 

1.  Size  of  Boilers,  and  surface  necessary  to  be  exposed  to  the 
fire.  —  In  adapting  the  boiler  of  a  hot-water  apparatus,  it  is  not 
necessary,  as  in  the  case  of  steam  boilers,  to  have  its  capacity 
exactly  in  proportion  to  the  quantity  of  pipe  that  is  attached  to 
it.  On  the  contrary,  it  is  sometimes  desirable  to  invert  this 
order,  and  to  attach  a  boiler  of  small  capacity  to  a  considerable 
length  of  pipe.  We  do  not  mean,  however,  in  recommending  a 
boiler  of  small  capacity,  to  propose,  also,  that  it  should  be  of 
small  superficies ;  for  the  efficiency  of  a  boiler  very  much  depends 
upon  the  quantity  of  surface  exposed  to  the  fire.  The  larger 
the  surface  exposed  to  the  action  of  the  calorific  influence,  the 
greater  will  be  the  economy  of  fuel,  and,  therefore,  the  greater 
will  be  the  effect  of  the  apparatus. 

In  proposing  the  adoption  of  boilers  of  small  capacity,  how- 
ever, it  is  necessary  to  accompany  the  recommendation  with  \ 
caution  against  running  into  extremes,  for  this  error  has  been 
the  cause  of  the  inefficiency  of  apparatus  in  many  instances. 
In  some  boilers,  we  have  seen  the  space  allowed  for  the  water 
so  very  small  that  the  boiler  was  thereby  rendered  completely 
useless. 

Too  small  a  quantity  of  water,  and  too  large  a  surface  exposed 
to  the  fire,  give  rise  to  various  evils,  among  which  are  the  depo- 
sition of  neutral  salts  and  alkaline  earths  by  the  water  which 
evaporates,  contracting  the  water-way,  and  impeding  circulation ; 
and  also  preventing  the  full  action  of  the  fire  on  the  exposed 
surface  of  the  boiler. 

But  perhaps  the  greatest  evil  arising  from  this  state  of  things, 

.is  from  the  repulsion  of  heat  by  the  metal  of  the  boiler.     The 

quantity  of  water  it   contains  being  so  small,  and  the  heat  of 

the  fire  very  intense  upon  it,  a  repulsion  is  caused  between 


HOT-WATER    BOILERS    AND    PIPES.  177 

the  iron  and  the  water,  and,  consequently,  the  latter  does  not 
receive  the  full  quantity  of  heat.  The  repulsion  between  heated 
metals  and  water  has  been  ascertained  to  exist,  even  at  low  tem- 
peratures, being  appreciably  different  at  various  temperatures 
below  the  boiling  point  of  water.  But  as  the  temperature  rises 
the  repulsion  increases  with  great  rapidity ;  so  that  iron,  when 
red-hot,  completely  repels  water,  scarcely  communicating  to  it 
any  heat,  except,  perhaps,  when  under  considerable  pressure. 

It  is  obvious  that  the  extent  of  surface  exposed  to  the  fire 
should  be  in  proportion  to  the  amount  of  water  contained  in  the 
boiler  and  the  pipes ;  and  it  is  easy  to  estimate  these  relative 
proportions  with  sufficient  accuracy,  notwithstanding  the  various 
circumstances  which  modify  the  effect.  Calculating  the  surface 
which  a  steam  boiler  exposes  to  the  fire  at  4  square  feet  for  each 
cubic  foot  of  water  evaporated  per  hour,  and  calculating  the 
latent  heat  of  steam  at  1000  degrees,  we  shall  find  that  the  same 
extent  of  boiler  surface  that  would  evaporate  a  cubic  foot  of 
water,  of  the  temperature  of  52°,  into  steam,  of  which  the  tension 
is  equal  to  one  atmosphere,  would  supply  the  requisite  heat  to 
232  feet  of  pipe,  4  inches  diameter,  when  its  temperature  is  to 
be  kept  at  140  degrees  above  that  of  the  surrounding  air.  The 
following  proportions  for  the  surface  which  a  boiler  for  a  hot- 
water  apparatus  ought  to  expose  to  the  action  of  the  fire,  will  be 
found  useful. 

Surface  of  boiler 
exposed  to  the  fire.  4  inch  pipe.     3  inch  pipe.     2  inch  pipe. 

3£  square  feet  will  heat    200  feet,  or    266  feet,  or    400  feet. 

5k       "       "      "       "      300         "        400         "        600     " 

7        "       "      "       "      400        «        533        "        800     " 

8i       "       "      "       "      500        "        666        "      1000     " 

12         "       "      "       «       700         «        933         "      1400     " 

17        "       "      "      "     1000        "      1333        "      2000     " 

A  small  apparatus  ought,  perhaps,  to  have  rather  more  sur- 
face of  boiler,  in  proportion  to  the  length  of  pipe,  than  a  larger 
one,  as  the  fire  is  less  intense,  and  acts  with  less  advantage,  than 
in  large  furnaces.  It  depends,  however,  upon  a  variety  of  cir- 
cumstances, whether  it  will  be  expedient  to  increase  the  quan- 
tity of  pipe,  in  proportion  to  the  surface  of  the  boiler,  beyond 


178  HOT-WATER    BOILERS    AND    PIPES. 

what  is  here  stated ;  for,  although  many  causes  tend  to  modify 
the  effect,  the  above  calculation  will  be  found  a  good  average 
proportion,  under  ordinary  circumstances.  The  effect  very  much 
depends  upon  the  quality  of  fuel,  the  force  of  draught,  the  con- 
struction of  the  furnace,  &c.,  which,  from  what  has  been  already 
said  on  these  matters,  will  show  that  they  will,  in  a  great 
measure,  influence  the  intensity  of  the  heat  received  by  the 
boiler.  It  is  always  safest,  however,  to  work  with  a  larger  sur- 
face of  boiler,  at  a  moderate  heat,  than  to  keep  the  boiler  Avork- 
ing  at  the  maximum  of  its  power. 

There  is  another  cause,  however,  that  will  tend  to  modify  the 
proportions  which  may  be  adopted.  The  data  from  which  the 
calculation  of  the  boiler  surface  is  made  assumes  the  difference 
to  be  140°  between  the  temperature  of  the  pipe  and  the  air  with 
which  it  may  be  surrounded ;  the  pipe,  in  this  calculation,  being 
200°,  and  the  air  60°.  But  if  this  difference  of  temperature  be 
reduced,  either  by  the  air  in  the  house  being  higher,  or  by  the 
apparatus  being  worked  below  its  maximum  temperature,  then, 
in  either  case,  a  given  surface  of  boiler  will  suffice  for  a  greater 
length  of  pipe.  For,  if  the  difference  of  temperature  between 
the  water  and  the  air  be  only  120°,  instead  of  140°,  the  same 
surface  of  boiler  will  supply  the  requisite  degree  of  heat  to  one 
sixth  more  pipe ;  and  if  the  difference  be  only  100°,  it  will  sup- 
ply one  third  more  pipe  than  the  quantity  stated  in  the  table. 

It  will,  therefore,  frequently  occur,  in  practice,  that  the  quan- 
tity of  pipe,  in  proportion  to  a  given  surface  of  boiler,  may  be 
considerably  increased  beyond  the  amount  which  is  given  in  the 
preceding  table ;  because,  in  forcing-houses,  the  temperature  of 
the  air  may  sometimes  be  above  the  number  of  degrees  here 
given,  and  frequently  the  temperature  of  the  water  may  be  below 
100°, — the  pipe  not  being  required  to  be  worked  at  its  full  heat; 
and,  therefore,  in  both  these  cases,  a  larger  proportion  of  pipe 
may  be  worked  by  a  given  sized  boiler. 

In  order  to  estimate  the  quantity  of  surface  which  is  acted 
upon  by  the  fire,  an  allowance  must  be  made  for  the  flues  which 
circulate  round  the  exterior  of  the  boiler,  (and  all  boilers  should 
be  so  erected  as  to  admit  of  the  action  of  the  heat  round  their 
sides.)  Thus,  suppose  an  arch  boiler  (Fig.  35)  to  be  30  inches 


HOT-WATER    BOILERS    AND    PIPES. 


179 


Fig.  35. 


long,  there  will  be  about  8£-  square  feet  of  surface  exposed  to  the 
fire,  that  is,  to  its  direct  action  underneath ;  and  suppose,  also, 
that  there  are  four  external  flues,  one  on  each  side,  —  or  sup- 
posing that  the  flue  went  all  round  the  boiler,  top  and  all,  —  we 
may  calculate  that  nearly  one  half  of  the  effect  is  produced  by 
these  flues  which  would  have  been  obtained  had  the  direct  action 
of  the  fire  been  employed  on  a  like  extent  of  surface ;  therefore 
the  flues  will  be  equal  to  5  square  feet,  making  altogether  13| 
square  feet  as  the  available  heating  surface  of  a  boiler  of  this  shape 
and  size,  which  we  consider  far  superior  to  the  old  form  of  boiler, 
as  shown  in  the  following  cut,  (Fig.  36.)  A  boiler  of  the  size 

Fig.  36. 


here  described  (Fig.  35)  would  be  sufficient  to  heat  about  800 
feet  of  pipe,  4  inches  diameter,  when  the  excess  of  its  tempera- 
ture above  that  of  the  surrounding  air  is  140°,  as  before  stated : 
a  boiler  of  the  same  shape,  24  inches,  has  about  11  square  feet 
of  surface  directly  acted  upon  by  the  fire ;  one  36  inches  long 
has  16£  square  feet  of  surface ;  and  one  42  inches  long  has  19 
square  feet  of  surface ;  the  increase  being  directly  proportioned 

in  the  simple  ratio  to  the  length. 
IB 


180  HOT-WATER    BOILERS   AND   PIPES. 

A  circular  boiler,  30  inches  diameter,  with  a  9  inch  circular 
flue  running  round  the  outside,  will  expose  nearly  the  same 
extent  of  surface  to  the  fire  as  the  one  just  described,  (Fig.  35,) 
both  being  the  same  length,  and  therefore  the  one  will  be  as 
effective  as  the  other ;  a  slight  diminution  on  the  perpendicular 
length  of  the  curve  makes  but  little  difference  to  its  capacity  for 
radiating  caloric. 

The  surfaces  of  any  size  of  this  shaped  boiler  can  easily  be 
calculated  by  the  same  rule ;  but,  instead  of  varying  in  the  sim- 
ple ratio  of  the  length  or  diameter,  it  will  be  found  to  be  propor- 
tional to  the  square  of  the  diameter,  so  that  the  proportion  of 
surface  increases  more  rapidly  than  in  the  arched  boiler.  Thus, 
a  circular  boiler,  24  inches  diameter,  has  8J  square  feet  of  sur- 
face exposed  to  the  fire ;  a  30  inch  has  13f  square  feet ;  a  36 
inch  has  19f  square  feet ;  and  a  42  inch  has  26f  square  feet 
exposed  to  the  fire ;  the  small  sizes  having  proportionally  less 
surface,  and  the  large  sizes  more  than  the  high-arched  boilers. 

The  rules  which  are  here  given  regarding  boilers,  are  framed 
to  suit  common  occurrence,  arid  intended  to  guide  practical  men 
who  have  the  management  and  working  of  common  hot-water 
apparatus.  There  are  some  cases,  however,  where  apparatus 
of  great  magnitude  is  necessary,  in  which  these  rules  will  not 
apply  without  modification.  But  as  such  instances  are  com- 
paratively rare,  and,  moreover,  as  no  person  that  is  a  novice  in 
the  practical  application  of  this  principle  of  warming,  will  be 
likely  to  undertake,  for  his  first  essay,  the  responsible  erection 
of  an  apparatus  of  great  dimensions,  it  is  the  less  necessary  to 
enter  at  length  into  such  cases  as  may  be  supposed  to  render 
any  alterations  of  these  principles  necessary. 

It  may,  however,  be  observed,  that  cases  may  occur  where  a 
peculiar  construction  of  apparatus  may  be  desirable ;  for  instance, 
where,  from  a  large  quantity  of  required  surface  a  furnace  of 
very  great  power  would  be  necessary ;  and,  in  that  case,  a  boiler 
which  exposes  a  large  surface,  while  it  possesses  but  a  small 
capacity,  would  obviously  be  injudicious,  because  the  intense 
heat  acting  on  a  small  body  of  water  would  probably  generate 
steam  to  a  high  degree  of  elasticity  in  the  boiler,  and  not  only 

I 


HOT-WATER    BOILERS    AND    PIPES. 


produce  much  inconvenience,  but  neutralize  the  effects  of  what 
might  otherwise  be  an  efficient  apparatus. 

The  nearer  the  rules  here  laid  down  for  regulating  the  size 
of  boilers  are  acted  upon,  the  more  efficient  will  be  the  working 
of  the  apparatus.  There  is  no  advantage  whatever  gained  by 
using  a  larger  boiler  than  is  necessary  to  heat  the  pipes  to  their 
maximum  temperature,  —  even  though  this  temperature  may 
never  be  required,  —  for,  as  the  return-pipe  should  (if  the  appara- 
tus be  working  right)  bring  in  a  fresh  supply  as  rapidly  as  the 
flow-pipe  takes  it  away,  the  boiler  is  always  kept  full.  It 
may  be  observed,  that  the  circulation  will  be  more  rapid  from  a 
minimum  boiler  than  from  a  maximum  one,  —  that  is,  from  a 
boiler  whose  capacity  is  rather  below  the  proportion ;  while  a 
boiler  whose  capacity  is  above  the  proportion  of  the  pipes,  has  a 
slower  circulation  ;  and  for  all  horticultural  purposes,  —  though 
the  former  has  some  little  advantage  in  the  time  of  heating  — 
the  latter  is  decidedly  to  be  preferred. 

In  the  following  section,  (Sect.  V.,)  further  information  will 
be  found  on  boilers,  etc.,  where  different  methods  of  heating,  in 
practical  operation,  are  figured  and  fully  described. 

We  may  here  state,  in  regard  to  the  material  for  boilers  for 
horticultural  purposes,  that  cast-iron  boilers,  if  properly  made, 
will  last  much  longer,  and  be  also  somewhat  cheaper  in  the  first 
instance,  than  malleable-iron  ones,  be  the  plates  ever  so  good ; 
the  principle  of  durability  resting  on  the  former  not  being 
injured  by  oxydation  so  much  as  the  latter.  In  both  cases, 
however,  the  durability  depends  very  much  on  the  kind  of  water 
used ;  that  least  liable  to  form  a  deposition  on  the  boiler  being 
the  best. 

2.  Size  and  arrangement  of  hot-water  pipes.  —  Some  contro- 
versy has  arisen,  among  engineers,  gardeners,  and  others,  respect- 
ing the  size  of  tube  most  suitable  for  the  purposes  of  heating 
hot-houses.  2,  3,  4,  5,  and  6  inch  pipes  have  been  used,  and 
experiments  instituted  respecting  the  merits  of  each ;  from  which 
it  has  been  found  that  4  inch  pipes  radiate  more  heat  than  any 
of  tKe  other  sizes ;  and,  consequently,  the  4  inch  pipes  are  now 
most  generally  used. 


182  HOT-WATER    BOILERS    AND    PIPES. 

The  unequal  rate  of  cooling  of  the  various  sizes  of  pipes, 
however,  renders  it  necessary  to  consider  the  purpose  to  which 
they  are  applied.  If  it  be  desired  that  the  heat  shall  be  retained 
for  a  great  many  hours  after  the  fire  is  extinguished,  then  pipes 
of  larger  dimensions  must  be  used.  Where  a  conservatory  is 
very  much  exposed,  and  liable  to  fall  below  the  minimum  tem- 
perature during  a  cold  night,  then  5  inch  pipe  may  be  used, 
which  will  retain  the  heat  longer  than  one  of  smaller  size  ;  but  a 
double  length  of  pipe  should  always  be  used  in  doubtful  cases. 
But,  as  a  general  rule,  no  pipe  should  be  used  of  more  than  4 
inches  diameter,  as  the  larger  the  pipe  the  greater  the  consump- 
tion of  fuel,  and  more  heat  will  be  given  out  by  4  inch  pipes,  in 
proportion  to  the  consumption  of  fuel,  than  by  pipes  of  any 
other  size. 

The  ordinary  method  of  arranging  hot-water  pipes  is  by 
placing  the  furnace  and  boiler  at  one  end  of  the  house,  and  lead- 
ing them  along  the  front  within  a  few  inches  of  the  wall.  If 
the  house  be  span-roofed,  the  pipes  ought  to  travel  completely 
round  both  sides ;  if  single,  or  lean-to  house,  the  pipe  should 
pass  along  the  front  and  return  the  same  way;  i.  e.,  the  flow  and 
return  pipes  should  be  placed  beside  each  other,  as  will  be  seen 
in  the  figures  in  the  next  section.  The  pipe  ought  never  to  run 
by  the  back  wall  of  a  house,  except  there  be  some  reason  to  fear 
the  entrance  of  frost  in  that  quarter,  which,  in  houses  with  thin 
walls,  or  those  constructed  with  clapboards,  is  quite  likely.  In 
general  cases,  the  heat  rises  with  sufficient  rapidity  from  the 
front,  to  prevent  the  entrance  of  frost  at  the  back  wall,  unless  it 
be  near  the  bottom  of  the  wall. 

In  general,  hot-water  apparatus  is  so  constructed  that  when 
the  smoke  leaves  the  boiler,  it  passes  immediately  up  the  chim- 
ney, by  which  an  incredible  amount  of  heat  is  lost.  I  have  seen 
the  thermometer  rise  to  200°  when  placed  at  top  of  a  chimney 
of  this  kind,  and  an  amount  of  heat  thereby  lost  nearly  equal 
to  the  whole  amount  radiated  in  the  atmosphere  of  the  house. 
This  is  the  case  with  many  heating  apparatuses,  without  the 
smallest  notice  being  taken  of  the  fact.  On  making  this  remark, 
lately,  to  a  most  intelligent  gardener,  he  doubted  the  fact  of 
losing  any  heat  by  his  chimney ;  while,  on  trying  the  thermome- 


HOT-WATER    BOILERS    AND    PIPES. 

ter  at  the  top  of  his  chimney,  we  found  it  rise  in  a  few  minutes 
to  137°,  after  having  travelled  through  20  feet  of  flue  through 
the  back  wall  of  the  house. 

Whatever  apparatus  be  employed  in  heating  a  hot-house,  the 
flue  should  always  be  taken  advantage  of.  It  must  be  remem- 
bered that  smoke  will  not  travel  through  a  flue,  —  neither  up 
nor  down,  —  without  first  being  rarefied  by  heat.  The  smoke, 
as  already  described,  is,  in  fact,  a  body  of  gases  emitted  from 
the  fuel  by  the  action  of  heat,  and  a  portion  of  this  it  takes 
along  with  it  on  leaving  the  furnace.  In  its  passage,  it  com- 
municates this  heat  to  other  bodies,  as  the  flue ;  and  more  so,  as 
the  flue  is  in  a  position  more  or  less  horizontal.  A  flue,  there- 
fore, should,  if  possible,  be  carried  the  whole  length  before  giving 
egress  to  the  smoke,  by  which  a  great  amount  of  fuel  may  be 
economized. 

In  laying  down  hot-water  pipes,  it  is  necessary  to  allow  suffi- 
cient room  for  their  elongation  and  expansion  when  they  become 
hot.  Want  of  attention  to  this  has  caused  several  accidents ;  for 
the  expansive  power  of  iron,  when  heated,  is  so  great,  that 
scarcely  anything  can  withstand  it.  The  linear  expansion  of 
cast-iron,by  raising  its  temperature  from  32°  to  212°,is  -0011111, 
or  about  one  nine  hundredth  part  of  its  length,  which  is  nearly 
equal  to  If  inches  in  100  feet.  Therefore,  it  is  necessary  to 
leave  the  pipes  unconfined,  so  that  they  shall  have  freedom  of 
motion  lengthways ;  and,  instead  of  confining,  as  has  frequently 
been  done,  facilities  should  be  provided  for  their  free  expansion, 
by  laying  them  on  small  rollers,  or  pieces  of  rod-iron,  between 
them  and  the  bearers  on  which  they  rest ;  for  the  contraction  on 
cooling  is  always  equal  to  the  expansion  on  heating,  and  unless 
they  can  readily  return  to  their  original  position  when  they 
become  cool,  the  joints  are  apt  to  become  loose  and  leaky,  as 
indeed  all  cast-iron  pipes  do,  that  are  exposed  to  sudden 
extremes  of  temperature. 

Every  hot-water  apparatus  should  be  provided  with  a  supply- 
cistern  attached  to  the  boiler,  or  the  pipes;  the  pipe  leading 
from  the  supply-cistern  should  flow  either  into  the  return-pipe, 
or  into  the  boiler,  near  the  bottom.  In  no  case  should  it  enter 
the  flow-pipe,  as  it  is  more  likely  to  emit  vapor,  and  the  steam, 
16* 


184  HOT-WATER     BOILERS    AND    PIPES. 

that  may  sometimes  be  generated  on  the  surface  of  the  water  in 
the  flow-pipe,  would  find  egress,  unless  the  supply-pipe  were 
bent  in  the  shape  of  an  CQ  to  prevent  it,  which  is  a  very  good 
plan ;  and,  as  a  small  lead  pipe  of  about  l£  inch  bore  is  suffi- 
cient to  supply  a  boiler  of  considerable  size,  the  pipe  can  easily 
be  bent  in  any  shape  to  answer  the  purpose. 

3.  Impediments  to  circulation,  fyc.  The  power  which  pro- 
duces the  circulation  of  the  water  in  the  pipes  is  the  specific 
gravities  of  the  two  bodies  in  the  return  and  flow-pipes ;  whether 
this  force  acts  on  a  pipe  100  feet  in  length,  or  on  one  only  5 
feet  in  length,  the  result  is  precisely  similar. 

Now  it  is  evident  that  if  this  unequal  pressure  is  the  vis  viva, 
or  motive  power,  which  sets  in  motion  the  whole  quantity  of 
water  in  the  apparatus,  in  order  to  ascertain  the  exact  amount 
of  this  force,  it  is  only  necessary  that  we  know  the  specific 
gravities  of  the  two  columns  of  water,  and  the  difference  will,  of 
course,  be  the  effective  pressure,  or  motive  power.  This  can  be 
accurately  determined  when  the  respective  temperatures  of  the 
water  in  the  boiler  and  in  the  descending  or  returning  pipe  are 
known. 

As  this  difference  of  temperature  rarely  exceeds  a  very  few 
degrees  in  ordinary  cases,  the  difference  of  the  weight  of  the  two 
columns  must  be  very  small.  But,  probably,  the  very  trifling 
difference  that  exists  between  them,  or,  in  other  words,  the 
extreme  smallness  of  the  motive  power,  is  very  imperfectly  com- 
prehended, and  will,  perhaps,  be  regarded  with  some  surprise, 
when  its  amount  is  shown  by  exact  computation. 

In  order  to  ascertain,  without  a  long  and  troublesome  calcula- 
tion, what  is  the  amount  of  motive  power  for  any  particular 
apparatus,  the  following  table  has  been  constructed.  An  appara- 
tus is  assumed  to  be  at  work,  having  the  temperature  in  the 
descending  pipe  170°,  and  the  difference  of  pressure  upon  the 
return-pipe  is  calculated,  supposing  the  water  in  the  boiler  to 
exceed  this  temperature,  by  from  one  to  twenty  degrees.  This 
latter  amount  will  exceed  the  difference  that  usually  occurs  in 
practice. 

By  referring  to  the  annexed  table,  it  will  be  found  that  when 


HOT-WATER    BOILERS    AND    PIPES. 


the  difference  between  the  temperature  of  the  flowing 
returning  columns  is  8  degrees,  the  difference  in  weight  is 
grains  on  each  square  inch  of  the  section  of  the  return- 
supposing  the  height  of  the  boiler  A  (Fig.  36,  / 

B)  to  be  12  inches.    This  height, however,  is/ 
only  taken  as   a   convenient   standard  from  I 
which  to  calculate;  for,  probably,  the  height \ 
may,  in  many  instances,  be  more  than  this,  \ 
though  it  will  seldom  be  less. 

Now,  suppose  that,  instead  of  12,  18 
inches  was  the  distance  between  the  two 
pipes,  that  is,  between  the  top  of  the  upper 
and  the  centre  of  the  lower  pipe,  and  the 
pipe  4  inches  in  diameter ;  if  the  difference  of 
temperature  between  the  water  in  the  boiler 
and  the  return-pipe  be  8  degrees,  the  pressure 
on  the  return-pipe  will  be  153  grains,  or 
about  one  third  part  of  an  ounce ;  and  this 
will  constitute  the  whole  amount  of  motive 
power  of  the  apparatus,  whatever  be  the 
length  of  pipe  attached  to  it.  If  such  an 
apparatus  have  100  yards  of  pipe  4  inches  in 
diameter,  and  the  boiler  contains,  say,  30  gal- 
lons of  water,  there  will  be  in  all  190  gallons, 
or  1900  Ibs.  weight  of  water,  kept  in  continual 
motion  by  a  force  equal  only  to  one  third  of 
an  ounce.  This  calculation  of  the  motive 
power  will  vary  under  different  circumstances ; 
and,  in  all  cases,  the  velocity  of  the  circula- 
tion will  vary  simultaneously  with  it. 


and 
8-16 

pipe, 


186 


HOT-WATER     BOILERS    AND    PIPES. 


Difference  in  weight  of  two  columns  of  water  each  one  foot  high,  at  various 
temperatures. 


Difference  in 

temp,  of  the 
two  columns 
of   water   in 

Difference  in  weight  of  two  columns  of  water  contained 
in  different  pipes. 

Difference  of 
a  column  one 
foot  high. 

degrees   of 

Fah.'s  scale. 

1  in.  diam. 

2  in.  diam. 

3  in.  diam. 

4  in.  diam. 

5  in.  diam. 

per  sq.  inch. 

2° 

grs.  weight 
1*5 

grs.  weight 
6-3 

grs.  weight 
14-3 

grs.  weight 

25-4 

grs.  weight 
33-6 

grs.  weight 

2.028 

4° 

3-1 

12-7 

28-8 

51-1 

110-1 

4-068 

6° 

4-7 

19-1 

43-3 

76-7 

211-7 

6-108 

8° 

6-4 

25-6 

57-9 

120-5 

250-0 

8-160 

10° 

8-0 

32-0 

72-3 

'  128-1 

317-5 

10-200 

12° 

9-6 

38-5 

87-0 

154-1 

376-1 

12-264 

14° 

11-2 

45-0 

101-7 

180-1 

390-9 

14-328 

16° 

12-8 

51-4 

116-3 

205-9 

449-1 

16-392 

18° 

14-4 

57-9 

131-0 

231-9 

522-0 

18-456 

20° 

16-1 

64-5 

145-7 

258-0 

700-0 

20-532 

The  above  table  has  been  calculated  by  the  formula  given 
with  table  IV.,  (see  Appendix,)  for  ascertaining  the  specific  grav- 
ity of  water  at  different  temperatures.  The  assumed  tempera- 
ture is  from  170°  to  190°. 

It  will  be  observed,  in  the  foregoing  table,  that  the  amount 
of  motive  power  increases  with  the  size  of  the  pipe ;  for  instance, 
the  power  is  four  times  as  great  in  one  of  4  inches  diameter  as 
in  one  of  2  inches,  and  nearly  six  times  as  great  in  one  of  5 
inches.  The  power,  however,  bears  exactly  the  same  relative 
proportion  to  the  resistance,  or  weight  of  water  to  be  put  in 
motion,  in  all  the  sizes  alike ;  for,  although  the  motive  power  is 
four  times  as  great  in  pipes  of  4  inches  as  in  those  of  2  inches, 
the  former  contains  four  times  as  much  water  as  the  latter. 
The  power  and  the  resistance  are,  therefore,  relatively  the  same. 

These  calculations  are  given  with  the  view  of  showing  how 
trifling  a  cause  may  impede  the  proper  circulation  of  the  hot 
water  in  pipes,  and  that,  when  once  obstructed,  how  impossible 
it  is  for  an  apparatus  to  work.  Trifling  as  this  power  may 
appear,  yet  upon  its  action  depends  entirely  the  efficiency  of  an 
apparatus.  Seeing  that  the  motive  power  is  so  small,  it  is  not 
surprising  that,  by  an  injudicious  arrangement  of  its  parts,  the 
motion  may  frequently  be  impeded  and  even  destroyed  ;  for  the 
slower  the  circulation  of  the  water,  the  more  likely  is  it  to  be 
interrupted  in  its  course. 


HOT-WATER    BOILERS    AND    PIPES.  187 

There  are  two  ways  by  which  the  motive  power  may  be 
increased.  One,  to  allow  the  water  to  cool  a  greater  number  of 
degrees  between  the  time  of  its  leaving  the  boiler  and  the  period 
of  its  return  through  the  descending  pipe.  The  other,  by 
increasing  the  vertical  height  of  the  ascending  and  descending 
columns.  The  effects  produced  by  these  two  methods  are  pre- 
cisely similar;  for,  by  doubling  the  difference  of  temperature 
between  the  flow  and  return  pipes,  the  same  increase  of  power 
is  obtained  as  by  increasing  the  vertical  height. 

There  are  two  methods  of  increasing  the  difference  of  temper- 
ature between  the  flowing  and  returning  pipes.  First,  by 
increasing  the  quantity  of  the  pipe,  so  as  to  allow  the  water  to 
flow  a  greater  distance  before  it  returns  to  the  boiler.  Secondly, 
by  diminishing  the  diameter  of  the  pipe,  so  as  to  expose  more 
surface  in  proportion  to  the  quantity  of  water  contained  in  it, 
and  by  this  means  to  make  it  part  with  more  heat  in  a  given 
time. 

The  first  of  these  methods,  although  the  most  practical,  is 
ncessarily  limited,  in  some  instances,  to  the  length  of  the  build- 
ing to  be  heated,  to  which  the  length  of  pipe  must  be  adjusted, 
in  order  to  obtain  the  required  temperature ;  and,  as  to  the 
second,  we  have  already  enumerated  many  objections  against 
the  use  of  small  pipes.  Where  the  motive  power,  therefore,  is 
not  of  sufficient  strength,  the  increase  of  the  height  of  the  col- 
umn ascending  from  the  boiler  must  be  depended  on  for  an 
additional  motive  power. 

In  all  cases,  the  rapidity  of  circulation  is  proportional  to  the 
motive  power,  and,  in  fact,  it  is  the  index  and  measure  of  its 
amount.  For,  if,  while  the  resistance  remains  uniform,  the 
motive  power  be  increased  in  any  manner,  or  in  any  degree, 
the  rapidity  of  circulation  will  increase  in  a  relative  proportion. 

Now,  the  motive  power  may  be  augmented,  as  we  have  seen, 
either  by  increasing  the  vertical  height  of  the  pipe,  by  reducing 
its  diameter,  or  by  increasing  its  length.  If,  by  any  of  these 
means,  the  circulation  be  doubled  in  velocity,  then,  as  the  water 
will  pass  through  the  same  length  of  pipe  it  did  before,  in  one 
half  the  time,  it  will  only  lose  half  as  much  heat  as  in  the  for- 
mer case,  because  the  rate  of  cooling  is  not  proportional  to  the 


188  HOT-WATER    BOILERS   AND   PIPES. 

distance  through  which  the  water  circulates,  but  to  the  time  of 
transit.  If,  then,  by  raising  the  pipes  vertically,  the  difference 
between  the  temperature  of  the  flow  and  return  pipes  be  in- 
creased, it  appears  to  be  the  most  practical  method  of  increasing 
the  velocity  of  motion.  The  increased  velocity,  therefore,  is 
indicative  of  increased  power,  and  in  a  hot-water  apparatus  it  is 
the  velocity  of  circulation  which  enables  it  to  overcome  any 
extraordinary  obstructions. 

Neither  the  principle  nor  the  practice  of  an  apparatus  is  in 
the  least  affected  by  having  an  additional  number  of  pipes  lead- 
ing out  of,  or  into,  the  boiler ;  the  effect  is  the  same,  whether 
there  be  more  flows  than  return  pipes,  or,  conversely,  more  return 
than  flow  pipes. 

4.  Level  of  Pipes.  —  Some  persons  have  supposed  that  if  the 
pipes  be  inclined  so  as  to  allow  a  gradual  fall  to  the  boiler  in  its 
return,  additional  power  is  gained.  This  appears  very  plausible, 
particularly  with  regard  to  some  forms  of  apparatus,  but  the 
principle  is  entirely  erroneous.  This  error  appears  to  arise  from 
treating  the  subject  as  a  simple  question  of  hydraulics,  instead 
of  a  compound  result  of  hydrodynamics.  If  the  question  were 
only  as  regards  a  fluid  of  uniform  temperature,  then  the  greatest 
effect  would  be  obtained  by  using  an  inclined  pipe;  but  the 
water  in  the  pipes  we  are  now  treating  of,  is  of  varying  density 
and  temperature,  which  very  materially  alters  the  results. 

Contrary  to  the  ideas  of  some  persons,  the  circulation  of  the 
water  first  takes  place  in  the  lower  pipe ;  in  consequence  of  the 
water  in  the  boiler  becoming  lighter  by  the  absorption  of  heat, 
the  column  of  water  in  the  return-pipe,  being  of  greater  density, 
forces  its  way  into  the  boiler,  when  the  water  in  the  upper  pipe 
falls  into  its  place.  Now,  suppose  the  distance  between  the 
entrance  of  the  return-pipe  and  that  of  the  flow-pipe  be  12  inches. 
This  distance  is  neither  increased  nor  diminished  by  any  incli- 
nation of  the  return-pipe  towards  the  boiler,  the  effective  pressure 
being  in  both  cases  the  same. 

Discarding  the  erroneous  hypothesis  that  the  motion  of  the 
water  commences  in  the  upper  pipe  instead  of  the  lower  one,  — 
and  the  motion  commences  at  the  entrance  of  the  lower  pipe  into 


HOT-WATER    BOILERS    AND    PIPES.  189 

the  boiler,  which  we  have  frequently  proved,  —  it  is,  therefore, 
evident  that  there  can  be  no  advantage  by  making  the  pipe  to 
incline  from  the  horizontal  level ;  for  whether  the  water  descends 
through  a  vertical  or  through  an  inclined  tube,  the  force  of 
gravity  will  only  be  equal  to  the  perpendicular  height ;  there 
must,  therefore,  be  an  equality  of  pressure  on  the  boiler  under 
all  circumstances,  whether  the  pipe  entering  the  boiler  be  on  a 
level,  or  inclined  from  its  junction  with  the  flow-pipe. 

When  it  is  necessary  to  sink  the  return-pipe  below  the  level 
of  the  boiler,  there  must  be  a  sufficient  weight  of  water  in  the 
pipes,  above  its  level,  to  overcome  the  perpendicular  column  that 
exists  below  the  level  of  the  boiler,  otherwise  the  tendency  of 
the  lower  column  will  be  to  a  retrograde  motion.  The  only  way 
is  to  raise  the  pipe  sufficiently  to  afford  a  perpendicular  return- 
ing column  of  sufficient  pressure  to  raise  the  water  in  the  per- 
pendicular pipe  attached  to  the  boiler. 

If  the  flow-pipe  be  carried  on  a  horizontal  level  with  the  boiler, 
and  the  return-pipe  carried  below  the  level  of  the  boiler,  it  is 
scarcely  possible  to  obtain  any  circulation ;  and  if  this  depth  be 
much,  no  circulation  at  all  can  be  obtained.  We  have  seen  some 
costly  apparatuses  completely  useless  on  this  account ;  and  those 
erectors  of  heating  apparatus,  unacquainted  with  the  principles 
of  hydrodynamics,  are  very  apt  to  commit  similar  mistakes. 
The  velocity  of  circulation  in  such  apparatus  will  be  just  in 
proportion  to  the  difference  of  weight  between  the  columns 
above  and  below  the  boiler. 

It  must  not  be  supposed  that  water  will  not  circulate  in  pipes 
below  the  level  of  the  boiler;  and  much  trouble  and  expense 
have  frequently  been  incurred  in  consequence  of  being  ignorant 
of  this  position.  All  that  is  necessary  is  to  give  the  upper  section 
of  pipe  a  sufficient  preponderance  to  raise  the  water  in  the  lower 
one,  allowing  for  the  superior  density  of  the  water  in  the  lower 
pipe.  It,  however,  requires  considerable  judgment  in  adopting 
any  such  forms  of  apparatus  as  this,  for  many  concurring  cir- 
cumstances are  essential  to  complete  success.  It  should,  there- 
fore, never  be  adopted  when  a  common  horizontal  working 
apparatus  can  be  introduced. 


190  HOT-WATER    BOILERS    AND    PIPES. 

5.  Accumulation  of  air  in  pipes.  —  It  is  necessary  to  make 
provision  for  the  escape  of  air  in  the  pipes,  which  sometimes  so 
accumulates  as  to  prevent  circulation.  This  is  more  especially 
the  case  when  the  apparatus  is  complicated,  and  has  many  turn- 
ings and  vertical  bends  in  the  pipes.  It  generally  collects  at  the 
upper  bends  of  the  pipe,  but  this  will  depend  very  much  upon 
the  mode  of  supplying  the  apparatus  with  water.  It  frequently 
requires  the  greatest  care  and  the  closest  attention  to  discover 
where  the  air  is  likely  to  lodge,  as  the  most  trifling  alteration 
in  the  position  of  the  pipes  will  entirely  alter  the  arrangements 
in  regard  to  the  air-vents.  Want  of  attention  to  this  has  been 
the  cause  of  many  failures,  and  the  discovery  of  the  places 
where  the  air  accumulates  is  sometimes  a  matter  of  difficulty. 
For  although  it  be  true,  in  a  general  sense,  that  air  will  rise  to 
the  highest  part  of  the  apparatus,  it  will  frequently  be  prevented 
from  getting  to  the  highest  part  by  alterations  in  the  level  of 
the  pipes,  and  by  other  causes. 

As  water,  while  boiling,  always  evolves  air,  it  is  not  sufficient 
merely  to  discharge  the  air  from  the  pipes  on  first  rilling  them, 
because  it  always  accumulates ;  and,  in  many  instances,  it  is 
desirable  to  have  the  air-vent  self-acting,  either  by  using  a  valve, 
or  small  open  pipe ;  but  we  have  generally  found  a  cock  most 
convenient. 

The  size  of  the  vent  is  not  material,  as  a  very  small  opening 
will  be  sufficient  to  allow  the  escape  of  air.  The  rapidity  of 
motion  in  fluids  is  inversely  proportional  to  their  specific  gravi- 
ties, as  water  is  827  times  more  dense  than  air ;  an  aperture 
which  is  sufficiently  large  to  empty  a  pipe  in  14  minutes,  if  it 
contained  water,  would  empty  it,  if  it  contained  air,  in  one 
second.  Air  being  so  much  lighter  than  water,  it  is  of  course 
necessary  that  the  vents  provided  for  its  escape  should  be  placed 
at  the  highest  parts  of  the  apparatus,  for  there  it  will  always 
lodge  when  no  impediment  occurs  to  prevent  it;  but  it  will 
sometimes  be  found  necessary  to  have  several  in  different  parts 
of  the  apparatus. 

Though  it  is  perfectly  easy  to  provide  for  the  discharge  of  the 
air  from  the  pipes,  —  as  far  as  the  mere  mechanical  operation  is 
concerned,  —  it  requires  much  consideration  arid  careful  study  to 


HOT-WATER    BOILERS   AND    PIPES.  191 

direct  the  application  of  those  mechanical  means  to  the  exact 
spot  where  they  will  be  useful.  We  have  frequently  seen 
mechanics,  who,  though  well  acquainted  with  the  practical 
details  of  the  apparatus  they  were  erecting,  yet  were  perfectly 
ignorant  of  the  principles  on  which  it  works ;  hence  the  success 
of  such  an  apparatus  must  be  entirely  a  matter  of  chance. 
Wherever  alterations  of  the  level  occur,  vents  should  be  pro- 
vided for  the  escape  of  air;  and,  as  we  have  said,  a  small  tap 
(or  cock)  will  be  the  most  convenient  method  of  outlet. 

In  a  complicated  arrangement  of  hot-water  apparatus,  it  is 
sometimes  so  very  difficult  to  detect  the  various  causes  of  inter- 
ference, and  the  impediments  which  arise  are  often  so  apparently 
insignificant  in  their  extent,  that  when  ascertained  they  are 
frequently  neglected.  Those,  however,  who  bear  in  mind  how 
very  small  is  the  amount  of  motive  power  in  any  apparatus  of 
this  description,  will  not  consider  as  unimportant  any  impedi- 
ment, however  small,  which  they  may  detect ;  moreover,  they 
will  immediately  see  the  propriety  of  having  the  evil  in  ques- 
tion put  right.  But,  in  the  more  complicated  forms  of  the 
apparatus,  so  many  causes  become  operative  in  impeding  the 
circulation,  that  the  real  cause  of  impediment  may  elude  the 
detection  of  even  an  experienced  practitioner. 

We  will  now  proceed  to  give  a  description,  in  detail,  of  various 
methods  of  heating,  which  come  within  the  range  of  our  own 
experience,  accompanying   the   descriptions  with  sketches,  by 
which  their  details  will  be  more  easily  understood. 
17 


SECTION    V. 

VARIOUS     METHODS     OF     HEATING     DESCRIBED     IN 
DETAIL. 

THE  heating  of  hot-houses,  by  any  of  the  ordinary  methods 
of  warming  these  structures,  has  hitherto  been  attended  with 
extravagant  expense.  The  difficulty  of  obtaining,  at  a  reason- 
able price,  the  means  of  keeping  up  the  desired  temperature, 
during  long  and  severe  winters,  —  the  expense  of  the  apparatus, 
—  the  annual  cost  of  repairs,  —  the  continual  outlay  for  fuel, — 
together  with  the  incidental  expenses  and  trouble  of  working 
them,  has,  in  many  instances,  proved  a  barrier  to  their  erection, 
and  has  induced  many  to  abandon  the  attempt,  who  had  well 
nigh  carried  it  into  execution.  Many  lovers  of  exotic  gardening 
have  thus  been  diverted  from  the  enjoyment  of  this  pleasant  and 
healthful  pursuit;  and  hence  it  is  of  the  utmost  importance, 
especially  to  amateurs  and  others  having  small  establishments, 
and  who  do  not  keep  a  regular  gardener,  that  the  internal  ar- 
rangements of  a  plant-house,  and,  above  all,  the  heating  arrange- 
ments, should  be  so  constructed  as  to  be  dependent  upon  the 
very  smallest  possible  amount  of  time  and  attention,  and  likely 
to  produce  the  least  injury  by  neglect. 

Among  the  numerous  systems  of  heating  lately  applied  to 
horticultural  buildings  in  England,  is  one  called  Polmaise,  from 
its  having  originated  at  a  place  in  Scotland  of  that  name,  —  the 
seat  of  the  late  Mr.  Murray,  near  Sterling.  The  principles 
upon  which  this  method  is  founded  are  not  new,  and  the  system 
itself,  in  other  modifications,  dates  from  a  period  much  more 
remote  than  any  other  with  which  we  are  acquainted.  This 
system  is  applied,  in  a  more  practical  and  perfect  form,  to  the 
warming  of  many  public  and  private  buildings  in  this  country. 
The  very  general  adoption,  however,  of  this  system,  does  not,  in 
the  smallest  degree,  give  us  a  warrant  against  its  defects.  It 


VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.      193 

has  been  ascertained  that  air  heated  to  a  temperature  of  300  de- 
grees, becomes  so  deprived  of  its  organic  matter,  and  otherwise 
changed  in  its  properties,  as  to  be  unfit  for  the  sustenance  of 
either  animal  or  vegetable  life,  in  a  state  of  healthy  and  vigorous 
development,  for  any  length  of  time ;  and  hence  the  admission 
of  a  current  of  highly  heated  air  into  a  dwelling  room,  or  into 
a  well  glazed  hot-house,  if  no  means  are  taken  to  restore  its 
original  properties,  must,  in  a  short  time,  become  sensibly  in- 
jurious to  the  animals  and  vegetables  that  are  compelled  to 
breathe  it. 

And  this  we  find  to  be  practically  the  case.  Every  gardener, 
on  entering  a  hot-house  so  heated,  is  immediately  sensible  of 
the  presence  of  contaminating  gases  in  the  atmosphere,  whether 
arising  from  the  combustion  of  fuel,  or  otherwise,  and  he  is  too 
well  acquainted  with  its  effects  on  vegetative  beings  to  allow 
his  tender  plants  to  absorb  it ;  hence  he  takes  immediate  meas- 
ures of  modifying  what  he  cannot  possibly  prevent.  It  can 
scarcely  be  doubted,  that  a  vast  amount  of  sickness  and  diseases 
of  the  respiratory  organs  is,  in  a  great  measure,  attributable  to 
the  same  circumstance,  especially  in  people  of  sedentary  habits, 
who  confine  themselves  to  close  chambers,  warmed  by  currents 
of  hot  air,  or  highly  heated  stoves.  The  latter,  in  this  respect, 
is  probably  worse  than  the  former ;  for,  in  the  one,  the  supply  of 
air  to  be  heated  is  drawn  from  the  external  atmosphere,  and, 
consequently,  is  less  likely  to  contaminate  the  air  of  the  room, 
although,  when  conducted  into  the  room  at  high  temperatures, 
the  atmosphere  of  the  latter,  without  egress  as  well  as  ingress 
of  air,  must  ultimately  become  so.  In  the  case  of  stoves,  how- 
ever, it  is  different,  for  by  them  the  same  atmosphere  is  heated 
over  and  over  again,  by  convection.  The  particles  of  air  in 
contact  with  the  stove  first  become  heated,  these  expand  with 
the  heat,  and,  consequently,  becoming  lighter,  rise,  and  the 
colder  particles  supply  their  place,  which  also  expand,  rise,  and 
are  in  their  turn  replaced  by  others.  Here  the  supply  of  air  to 
be  warmed  is  drawn  directly  from  the  room  itself;  thus  com- 
pelling the  inmates  to  inhale  the  same  contaminated  atmos- 
phere for  days  together,  without  mixture  or  admission  of  fresh 
air,  except  the  small  portion  that  finds  an  unwelcome  entrance 


194     VARIOUS   METHODS    OF    HEATING   DESCRIBED   IN    DETAIL. 

by  the  occasional  opening  of  the  door ;  and  in  the  severe  weather 
of  our  winters,  with  the  thermometer  below  zero,  this  portion  is 
frequently  small  indeed.  The  pleasure  and  ability  of  exercising 
our  physical  functions  in  cold  weather,  will  be  in  exact  propor- 
tion to  the  frequency  of  practice  ;  and  it  is  truly  surprising,  that 
with  so  much  positive  proof  of  direct  injury  resulting  from  con- 
tinued confinement  over  highly  heated  stoves,  many  will,  never- 
theless, persist  in  so  pernicious  a  custom,  —  a  custom  which  is 
truly  national,  and  which  renders  the  influence  of  these  stoves 
as  baneful  as  that  of  the  Upas  tree,  and  sends  thousands  an- 
nually to  an  untimely  and  premature  grave. 

I  have  observed,  by  some  articles  that  have  lately  appeared  in 
an  excellent  horticultural  periodical,  (Downing's  Horticulturist,) 
that  this  much  talked  of  system  of  warming  horticultural  struc- 
tures with  hot  air,  called  Polmaise,  has  been  adopted  by  some 
individuals  in  this  country.  These  individuals  have  been  misled 
by  the  extravagant  statements,  or  rather  raw-statements,  that 
have  from  time  to  time  appeared  in  the  Gardener's  Chronicle, 
(of  England,)  by  its  talented  editor  and  others  under  his  influ- 
ence. Those  who  have  been  in  the  habit  of  reading  that  paper 
in  this  country,  and  noticed  the  laudatory  articles  that  have  so 
frequently  appeared  in  it,  in  favor  of  this  method,  yet  unac- 
quainted with  the  practical  opposition  it  has  received  by  num- 
bers of  experienced  men,  in  every  way  qualified  to  decide  upon 
its  merits,  can  scarcely  be  blamed  for  adopting  a  system  said  to 
possess  so  many  advantages  over  all  others ;  and  when  it  is  con- 
sidered that  the  gardening  journal,  which  represents  the  opinions 
of  practical  men  in  that  country,  is  but  little  read  in  America, — 
in  fact,  I  may  say,  almost  unknown,  save  by  a  few  individuals, — 
it  is  not  surprising  that  they  should  have  been  betrayed  into  the 
system  supported  by  such  authority.  It  is  difficult,  indeed,  to 
account  for  the  strong-headed  and  one-sided  policy  of  the  advo- 
cates and  promoters  of  Polmaise.  The  fact  is  well  known,  that 
the  system,  and  the  defects  connected  with  it,  were  thoroughly 
established  many  years  before  it  was  applied  at  the  place  from 
which  it  takes  its  name.  In  many  places  it  had  been  tried,  and 
found  inferior,  and  far  more  fickle  than  the  common  smokf 


VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL.      195 

flue.^  It  originated  at  Polmaise  Gardens,  from  the  following 
circumstances :  —  A  church  in  the  neighborhood  of  that  place 
had  been  warmed  by  a  hot-air  furnace,  similar  to  those  used  in 
dwelling-houses  in  this  country.  A  gardener  at  that  place 
examined  it,  and  thought  it  a  good  plan  to  warm  his  hot-houses ; 
accordingly,  he  applied  something  of  the  same  kind  to  heat  his 
vinery.  The  thing  was  entirely  new  to  the  worthy  gardener, 
as  well  as  to  his  employer,  who  sent  an  account  of  it  to  Dr. 
Lindley,  of  the  Gardener's  Chronicle,  who  forthwith  espoused 
the  system,  extolled  it  to  the  skies,  and  induced  various  individ- 
uals to  adopt  it ;  and  those  who  would  not,  he  straightway  de- 
nounced as  interested  and  dishonest  men.  The  gardening  com- 
munity arose  in  arms,  and  waged  war  against  their  theoretical 
foes,  until  its  so-called  originators  were  confounded  at  the  amount 
of  opposition  excited.  No  controversy  connected  with  gardening 
was  ever  carried  on  with  so  much  virulence  as  this  one  on  Pol- 
maise heating ;  and  no  system  has  been  so  severely  tested,  to 

*  The  premature  encomiums  so  liberally  lavished  upon  this  system,  by 
the  zeal  of  its  promoters,  have  neither  shamed  imposture  nor  reclaimed 
credulity.  Deceptions  seldom  stand  long  against  acpurate  experiments, 
and  the  mere  charm  of  novelty  soon  vanishes,  when  economy  and  util- 
ity are  both  against  it.  The  desire  of  notoriety,  if  nothing  else,  has  too 
often  induced  parties  to  impose  on  the  credulity  of  those  who  have  not 
science  enough  to  investigate  its  principles,  nor  practice  enough  to  dis- 
cover its  defects.  Nothing  can  more  plainly  show  the  necessity  of  doing 
something,  and  the  difficulty  of  finding  something  to  do,  to  obtain  these 
paltry  ends,  than  the  getting  up  of  this  method  of  heating  hot-houses  ; 
and  this,  too,  by  those  who  know,  or  ought  to  know,  better,  and  who 
ought  to  have  rejected  it  with  contempt.  When  a  system  has  no  intrin- 
sic value,  it  must  necessarily  owe  its  attractions  to  theoretical  embellish- 
ment, and  catch  at  all  advantages  which  the  art  of  writing  can  supply. 
Trifles  always  require  exuberance  of  ornament ;  the  building  which  has 
no  strength  or  utility,  can  be  valued  only  for  the  novelty  of  its  charac- 
ter, or  the  money  which  it  cost.  It  is  certain  that  the  advocate  of  a 
new  system  is  less  satisfied  by  its  failure,  than  its  success,  even  when 
no  part  of  its  failure  can  be  imputed  to  himself,  and  when  the  fruits  of 
his  labor  are  tested  by  those  who  can  discover  their  real  worth.  No 
man  has  a  right,  in  things  admitting  of  gradation,  to  throw  the  whole 
odium  upon  his  opponents,  and  totally  to  exclude  investigation  and  in- 
quiry, by  a  haughty  consciousness  of  his  own  excellence. 

17* 


196     VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL. 

prove  its  worth.  Gardeners,  amateurs,  and  all,  entered  the  arena 
of  experiment  and  discussion.  Still  its  promoters  would  not 
flinch  from  their  original  position,  and,  right  or  wrong,  would 
cram  it  down  gardeners'  throats,  whether  it  was  digestible  or 
not;  and  that,  too,  without  one  tittle  of  evidence  in  favor  of  it, 
except  ripe  grapes  in  September,  —  a  period  when  grapes  would 
ripen  themselves,  without  any  artificial  heat  at  all.  Yet  its 
cheapness  and  simplicity  were  its  recommendation,  and  for 
some  successive  winters  many  went  to  work  Polmaising  their 
hot-houses,  tearing  down  their  furnaces,  flues,  &c.,  and  con- 
verting them  into  Polmaise  stoves,  hot-air  drains,  and  other 
appurtenances  of  Polmaise  ;  but,  after  a  short  trial,  and  a  good 
deal  of  plant-killing,  they  one  and  all  abandoned  the  sys- 
tem with  disgust.  Still,  amidst  all  this  dust  and  dirt,  and 
smoke  and  gas,  created  by  the  cracking  of  plates  and  the 
breaking  of  tiles,  the  Doctor  maintained  his  ground,  until,  like 
the  conquered  hero,  he  was  left  alone  in  his  glory,  in  the 
midst  of  the  wreck  and  ruin  he  had  created.  What  seems  very 
strange,  he  never  erected  one,  or  caused  one  to  be  erected,  at 
the  Horticultural  Society's  garden,  where  he  had  unlimited  con- 
trol, and  ample  opportunity  of  so  doing ;  and  those  who  erected 
them  by  his  recommendation  and  advice,  were  obliged  to  ac- 
knowledge them  unqualified  failures,  notwithstanding  all  their 
alterations  and  improvements  upon  the  original  plan,  which  was 
simply  this  :  —  A  hot-air  furnace  is  placed  behind  the  back  wall, 
about  the  centre  of  the  house;  immediately  opposite  the  stove 
there  is  an  aperture  in  the  wall,  for  the  admission  of  the  heated 
air  into  the  house  ;  directly  in  front  and  above  this  aperture,  a 
woollen  cloth  is  suspended,  which  is  kept  constantly  moist  by  a 
number  of  worsted  skeins  depending  from  a  small  gutter,  fixed 
on  a  frame  of  wood,  which  supports  both  the  gutter  and  the 
cloth,  the  lower  end  of  the  latter  reaching  the  ground.  The 
cloth  is  made  thicker  in  the  middle,  in  order  to  equalize  the 
heat,  —  an  arrangement  which  is  absolutely  necessary ;  for  if  the 
cloth  was  an  equal  thickness  all  over,  the  centre  of  the  house 
would  be  heated  to  a  scorching  degree,  (by  the  rush  of  hot  air,) 
while  the  ends  would  be  comparatively  cold.  By  means  of 
drains  under  the  floor,  the  fire-place  is  supplied  with  air  from 


VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.       197 

Fig.  37. 


a 


198     VARIOUS   METHODS    OF    HEATING   DESCRIBED    IN    DETAIL. 

inside  the  house,  part  of  which  is  used  for  the  combustion  of 
fuel ;  the  rest  passes  over  the  heated  stove  and  enters  the  house 
through  the  apertures  above  noticed. 

Fig.  38. 


Such  is  the  original  system  of  Polmaise  heating,  which  has 
created  so  much  sensation  in  England,  but  which  is  now  aban- 
doned for  some  one  or  other  of  the  many  improved  methods  to 
which  it  gave  rise,  the  most  perfect  and  scientific  of  which,  I 
have  represented  in  the  accompanying  cuts,  Figs.  37,  38,  and  39. 
The  arrows  marked  a,  in  the  three  figures,  show  the  entrance  of 
the  cold  air  from  the  external  atmosphere ;  and  its  passage  to 
the  fire-place,  beneath  the  floor  of  the  house,  is  further  shown 
by  the  arrows  b,  in  Figs.  37,  38,  and  39.  Its  passage  over  the 
hot  plate,  through  the  chamber,  under  the  bed,  and  thence  into 
the  house,  is  marked  by  c,  attached  to  each  arrow  in  the  three 
figures ;  d,  the  fire-place ;  e,  a  tank  containing  water,  imme- 
diately over  the  cast-iron  plate ;  /,  a  small  funnel,  or  tube,  for 
supplying  water  to  the  tank ;  g,  (Fig.  38,)  shows  the  bed  on 
which  the  plants  are  placed,  resting  on  cross-bars,  and  filled 
with  pieces  of  brick,  having  a  layer  of  sand  or  sawdust  on  top ; 
this  can  be  converted  into  a  stage,  if  desired.  This  is  Mr. 
Meek's  modification  of  Polmaise,  from  whom  the  drawing  ap- 
peared in  the  Gardener's  Chronicle,  and  was  there  represented 
as  something  very  near  perfection  in  heating,  if  not  perfection 
itself.  The  above  sketch  is  somewhat  altered  and  simplified  in 


VARIOUS   METHODS   OF   HEATING   DESCRIBED   IN    DETAIL.      199 


D 


the  formation  of  the  drains;  and  yet, 
in  all  conscience,  it  is  complex  and 
compound  enough  for  a  heating  appa- 
ratus, as  any  person  can  see  by  a  glance 
at  the  above  sketches.  It  is  difficult  to 
discover  wherein  lies  its  superiority 
over  the  old  smoke-flue,  and  it  is 
clearly  evident,  that  it  has  neither 
cheapness,  simplicity,  nor  economy  in 
fuel,  to  recommend  it;  and,  as  to  its 
working,  it  is  infinitely  more  precarious 
than  the  common  flue,  and  the  loss  of 
heat  is  certainly  much  greater.  This 
loss  has  been  stated,  by  those  who  have 
tested  its  merits,  to  be  at  least  one 
fourth  of  its  whole  heating  power.  Mr. 
Ayres,  one  of  the  most  enlightened 
gardeners  in  England,  stated,  in  a  paper 
on  that  subject,  published  in  the  Gar- 
dener's Journal  of  1847,  that  Mr.  Meek 
wasted  more  heat  from  his  one  house, 
than  he  (Mr.  Ayres)  did  from  one  fire 
that  had  nine  different  arrangements  to 
work;  and  in  a  Polmaise  apparatus  that 
Mr.  Ayres  had  erected,  the  waste  of 
heat  was  enormous ;  that  in  ten  min- 
utes after  the  fire  was  lighted,  he  could 
ignite  a  piece  of  paper  at  the  top  of  the 
chimney  with  the  greatest  ease;  and 
when  the  same  gentleman  asked  one 
of  its  strongest  advocates  the  following 
question,  "  If  you  had  a  range  of  houses 
to  heat  in  the  best  possible  manner, 
would  you  abandon  hot  water  for  Pol- 
maise ?  "  he  was  answered,  "  No,  cer- 
tainly not." 

I  have  quoted  the  opinion  of  Mr.  Ayres,  because  he  is  well 
known  to  be  one  of  the  best  authorities  on  matters  of  practical 


D 


200     VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

importance,  connected  with  horticulture,  at  the  present  day,  and 
his  opinions  are  endorsed  by  almost  every  gardener  of  note  in 
England.  Mr.  Fleming,  of  Trentham,  and  Mr.  Paxton,  of 
Chatsworth,  as  well  as  many  others,  regarded  it  as  a  thing  ut- 
terly unworthy  of  notice.  Mr.  Ayres,  in  the  same  paper  already 
quoted,  puts  to  the  advocates  of  Polmaise  the  following  conclu- 
sive and  unanswerable  query.  If  Dr.  Lindley,  or  any  other  of 
its  advocates,  can  point  to  one  place  where  the  apparatus  is  at 
work,  and  as  efficacious  as  a  hot-water  apparatus ;  if  they  can 
refer  us  to  any  one  place,  where  we  can  see  better  productions 
than  what  have  resulted  from  the  use  of  hot  water,  why,  says 
he,  I  am  ready  to  spend  five  sovereigns  to  go  to  see  it,  and  be 
convinced  of  my  error  in  opposing  it ;  bat  until  then,  it  is  mere 
nonsense  to  suppose  that  any  responsible  person  will  adopt  it. 

As  an  example  of  a  combination  of  hot  water  and  hot  air, 
applied  in  a  practical  and  scientific  manner,  the  following  sys- 
tem is  superior  to  any  other  with  which  I  am  acquainted,  espec- 
ially for  small  houses.  It  supplies  heat,  moisture  and  air,  either 
singly  or  combined.  It  consists  of  a  cast  or  plate  iron  boiler,  0, 
for  containing  the  water ;  in  shape  it  is  not  unlike  a  pretty  large 
inverted  flower-pot,  with  a  hollow  between  its  sides,  about  four 
or  five  inches  wide,  having  one  pipe  entering  near  the  top  for 
the  flow,  and  another  at  the  bottom  for  the  return,  with  a  tube 
entering  quite  through  to  the  fire-chamber,  as  represented  at  b, 
c,  and  d ;  then  there  is  a  hot-air  chamber  round  the  boiler  and 
fire-place,  as  shown  at  e,  e,  e,  Figs.  A,  B,  and  C  ;  the  boiler 
rests  on  a  circular  course  of  bricks,  forming  the  furnace/,/, 
Figs.  B  and  C.  The  whole  is  enclosed  by  the  hot-air  chamber, 
from  which  the  air  is  conducted  into  the  house,  at  k,  and  is 
supplied  with  cold  air,  both  for  the  combustion  of  fuel,  and 
drawing  off  the  heated  air,  at  i,  i,  Fig.  C.  The  fire  is  fed 
through  the  door  in  the  chamber,  j,  opposite  which  is  a  smaller 
door  in  the  furnace,  at  k.  In  Fig.  C  is  shown  the  door  of  the 
ash-pit,  Z,  through  which  the  ashes  are  drawn.  We  know  of  no 
apparatus,  where  a  small  green-house  or  conservatory  is  required 
to  be  heated,  that  will  do  it  so  effectually  and  economically  as 
this.  No  particle  of  heat  generated  is  lost,  and  in  its  simplicity 
is  everything  that  a  novice  could  desire.  Here  is  nothing  more 


VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL.       201 


Fig.  40. 


202      VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

than  a  cone  of  cast  or  plate  iron,  with  hollow  sides,  one  hole 
for  a  flow,  and  one  for  a  return  pipe,  (these  pipes  can  branch 
into  several  directions,  if  necessary,  on  leaving  the  boiler,)  and 
a  channel  through  it,  with  a  flange,  or  neck,  on  which  to  fix  the 
smoke  pipe ;  build  the  boiler,  thus  formed,  on  a  fire-place,  with 
just  distance  sufficient  below  the  edge  of  the  cone  for  a  door,  to 
supply  fuel ;  this  door  should  be  quite  narrow,  in  order  to  let 
the  edge  of  the  boiler  as  far  down  as  possible.  The  hot-air 
chamber  should  be  built  of  brick,  and,  if  exposed  to  the  atmos- 
phere, should  be  at  least  one  foot  thick.  In  fact,  the  thicker 
the  wall  of  the  hot-air  chamber  is  made,  the  better  will  the 
heat  be  retained.  A  tank  of  water  is  placed  over  the  hot-air 
entrance,  inside  the  house,  for  evaporation.  If  this  system  be 
not  bungled  in  the  construction,  it  will  be  found  as  cheap  as 
any  other,  and  the  expenditure  for  fuel  is  but  trifling.  The  cir- 
culation of  the  water  is  complete,  and  the  air  in  the  chamber  is 
neither  roasted  nor  burned,  as  it  is  chiefly  received  through  the 
boiler,  and,  consequently,  is  possessed  of  more  natural  purity, 
which  is  so  essential  to  vegetable  life ;  and  it  requires  so  little 
attention  that  any  amateur  can  manage  it  without  much  trouble. 
Even  in  pretty  severe  weather,  when  set  fairly  agoing  in  the 
evening,  it  wants  no  more  attention  till  morning ;  set  it  right  in 
the  morning,  and  you  may  safely  leave  it  again  till  night.  Nor 
is  it  liable  to  accident  or  derangement.  Not  the  least  of  its 
recommendations  is  its  economy  of  fuel,  —  a  circumstance  of  con- 
siderable importance,  especially  where  the  cost  of  fuel  is  high ; 
and,  therefore,  the  economy  thereof  is  of  double  moment  to  the 
proprietor. 

We  have  never  seen  this  system  applied  to  large  structures,  but 
we  have  no  doubt,  were  the  apparatus  made  in  proportion  to  its 
work,  it  would  answer  as  well  in  large  as  in  small  houses ;  at 
all  events,  there  is  no  reason  why  furnaces  and  boilers  of  every 
description  should  not  be  chambered  round  in  a  similar  way  ; 
a  very  great  amount  of  heat,  that  is  now  lost,  would  be  turned  to 
advantage,  and  I  think  it  is  not  too  much  to  say,  that  hot-houses 
could  be  heated  at  one  half  the  expenditure  of  fuel. 

The  system  of  heating  two,  three,  or  more,  houses  with  one 
boiler,  is  one  of  those  valuable  improvements  which  science, 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         203 

combined  with  mechanical  ingenuity  has  devised,  and  which 
has  been  carried  out  in  practice  with  the  most  gratifying 
success,  —  so  much  so,  that  in  some  places,  separate  apparatuses 
have  been  torn  down,  and  this  system  adopted  instead,  merely 
on  account  of  the  fuel  economized  thereby.  Among  the  many 
systems  brought  before  the  public,  under  the  fine-sounding  name 
of  improved,  it  is  doubtful  whether  any  of  them  have  given  so 
entire  satisfaction  as  the  above,  where  it  has  been  properly  con- 
structed. The  facility  so  admirably  afforded  by  this  method  of 
heating  any  of  the  connected  houses  in  the  space  of  a  few  min- 
utes after  it  is  found  necessary,  is  certainly  a  great  recommen- 
dation in  its  favor.  In  short,  you  have  only  to  turn  a  tap,  and 
the  thing  is  accomplished.  Fig.  41  represents  the  ground  plan 
of  four  houses  heated  in  this  way,  and  most  efficiently. 

It  will  be  seen  from  the  plan,  that  the  two  end  houses  on  the 
front  are  heated  by  the  pipes  flowing  and  returning  into  the 
pipes  which  supply  the  hot  water  for  the  two  houses  standing  on 
the  back.  This  is  easily  accomplished  by  having  a  tap  on  each 
pipe  where  it  enters  the  house,  so  that  either  house  may  be 
heated,  or  both  together,  if  required. 

In  the  extensive  forcing-establishment  of  Mr.  Wilmot,  at  Isle- 
worth,  near  London,  no  less  than  seven  ranges  of  houses,  each 
ninety  feet  in  length,  are  heated  by  one  boiler,  and  all  are  heated 
effectually,  and  that  too  for  the  purpose  of  forcing  grape-vines. 
In  many  other  places,  in  England,  we  know  that  this  method 
has  been  adopted  with  the  very  best  results. 

In  the  plan  here  given,  the  box,  (Fig.  42,)  which  is  given  on  a 
larger  scale,  is  situated  immediately  over  the  boiler.  It  may, 
however,  be  on  the  same  level,  or  nearly  so,  a*id  situated  in  any 
corner  out  of  the  way.  The  boiler  here  used  is  a  common  saddle 
boiler,  and  with  a  large  apparatus,  is  probably  the  best  boiler 
for  general  purposes.  The  apartments,  g  g,  in  the  cut  (Fig.  41) 
are  offices  for  the  garden,  tool-house,  potting-room,  fruit-room, 
&c.,  and  may  be  used  as  a  mushroom-house.  As  the  hot-water 
pipes  pass  through  them,  they  are  kept  slightly  warmed,  and 
may  be  made  useful  as  store-rooms  and  other  kinds  of  garden 
offices. 

In  some  places  in  England,  no  less  than  eight  or  ten  different 
18 


204       VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 


I 


6 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         205 
Fig.  42. 


departments  are  heated  by  one  boiler ;  some  of  them  going  at 
one  time,  and  some  at  another,  and  sometimes  all  going  together, 
and  each  having  abundance  of  heat.^  The  convenience  of  this 
system  cannot  be  too  highly  appreciated,  especially  when  there 
are  a  number  of  small  plant-houses  situated  near  each  other. 
For  instance,  suppose  the  boiler  to  be  at  work  for  one  of  the 
houses,  which  may  be  a  plant-stove  or  forcing-house ;  well,  you 


Fig.  B. 


*  Fig.  B  shows  the  common  method  of  placing  supply-cisterns.  They 
may  be  placed  in  some  convenient  situation  and  attached  by  a  small 
pipe  to  the  apparatus.  To  prevent  the  escape  of  vapor,  it  is  desirable 
to  bend  the  pipe  into  the  form  shown  at  a  b,  as  the  water  in  the  part  of 
the  inverted  syphon  at  a,  will  remain  quite  cold. 


206        VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL. 

go  out  before  bed-time,  and  find  the  sky  clear  and  frosty,  con- 
trary to  your  anticipations  in  the  early  part  of  the  evening,  — 
and  how  often  do  we  find  this  really  to  be  the  case,  —  you  enter 
into  your  green-house,  and  you  find  the  thermometer  travelling 
down  rather  quickly  towards  the  freezing-point.  Kindling  fires 
is  generally  an  unpleasant  business  at  this  time  of  night,  and 
we  are  pretty  often  inclined  to  let  the  plants  take  their  chance, 
rather  than  be  at  the  trouble  of  doing  it,  even  if  it  should  cost 
us  half  a  night's  sleep  through  anxiety.  Here,  this  unpleasant 
business  is  dispensed  with,  and  the  anxiety  too,  as  well  as  the 
sitting  up  till  the  house  is  heated  arid  safe  for  the  night.  You 
go  to  the  tank  or  box,  which  is  generally  situated  so  as  to  be 
easily  got  at,  in  a  recess  made  in  the  wall,  perhaps,  or  immedi- 
ately over  the  boiler,  as  represented  in  Fig.  A ;  but,  in  any  case, 
it  should  be  so  arranged  as  to  be  always  of  easy  access  from  the 
houses.  The  arrangement  of  the  pipes  makes  no  difference, 
providing  the  accumulating  tank  be  sufficiently  elevated.  The 
moment  the  water  is  put  on,  the  circulation  commences;  in 
flows  a  delightful  stream  of  hot  water,  warming  the  pipes  as  it 
proceeds  through  the  flow  and  return;  a  vivifying  glow  of 
warmth  pervades  the  chilly  atmosphere  of  your  green-house,  and 
you  can  retire  to  rest  without  being  troubled  with  anxious 
thoughts  about  your  plants,  let  the  weather  turn  as  it  may. 

It  may  appear,  that,  by  this  arrangement,  a  larger  quantity  of 
fuel  will  be  required  for  a  single  house,  than  if  that  house  had 
an  apparatus  for  itself.  Not  so,  however ;  for,  by  close  observa- 
tion, it  is  found  that  the  consumption  of  fuel  is  pretty  nearly  in 
proportion  to  the  water  heated,  and  that  the  heat  given  off  by 
the  pipes  is  in  direct  ratio  to  the  heat  absorbed  by  the  boiler 
from  the  fire.  Thus,  if  one  house  only  be  at  work,  there  is  only 
the  water  of  one  arrangement  to  be  heated ;  and,  consequently, 
only  one  return  of  cold  water  into  the  boiler,  the' rest  being  shut 
off.  Now,  if  the  water  be  shut  off  into  the  box,  that  is,  the 
mouths  of  the  flow-pipes  stopped,  there  is  no  circulation ;  hence, 
there  is  no  return  of  the  cold  water  into  the  boiler,  and,  conse- 
quently, no  absorption  of  caloric  or  combustion  of  fuel.  Of 
course,  more  fuel  is  required  to  heat  the  four  houses,  than  would 
be  required  to  heat  one,  for  the  reasons  stated,  that  the  larger 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         207 

the  body  of  cold  water  flowing  into  the  boiler,  and  the  larger 
the  body  of  warm  flowing  from,  it,  the  more  heat  is  carried 
away ;  hence,  the  more  specific  caloric  is  required,  and  the  more 
combustion  of  fuel  to  produce  it.  But  the  proportion  of  fuel 
consumed  to  the  proportion  of  heat  generated  by  the  pipes  is 
found  to  decrease  as  the  radiating  surface  is  increased.  This 
decrease  amounts  to  nearly  one  third ;  for  it  is  found  that  eight 
separate  houses,  or  departments  of  a  house,  can  be  heated  by  the 
same  quantity  of  fuel  which  it  formerly  required  to  heat  five. 
This  calculation  was  supplied  to  me  by  an  intelligent  gardener, 
of  extensive  experience,  who  made  it  from  strict  investigation 
into  the  working  of  the  system  under  his  own  charge ;  and  the 
statement  is  corroborated  by  the  fact,  that  no  case  has  occurred, 
to  my  knowledge,  among  many  with  which  I  am  acquainted,  and 
have  examined,  that  has  failed  to  give  satisfaction. 

This  system  has  not  the  complex  character  which  some  have 
assigned  to  it,  and  which,  at  first  sight,  it  would  appear  to  pos- 
sess ;  and,  as  to  its  cheapness,  I  believe  little  can  be  said  about 
it,  when  placed  in  comparison  with  other  hot-water  apparatuses. 
I  have  had  no  means  of  calculating  the  difference,  if  any, 
between  this  apparatus  and  as  many  single  ones  as  it  may  be 
substituted  for.  But  it  certainly  appears,  that  four  houses 
heated  with  one  boiler  and  one  furnace,  would  be  cheaper  than 
four  houses  heated  with  four  distinct  boilers  and  furnaces,  the 
quantity  of  piping  in  both  cases  being  equal ;  for  then,  three 
boilers  and  furnaces,  or  the  cost  of  them,  would  be  saved.  This 
difference,  however,  will  depend  very  much  upon  the  distance 
the  pipes  must  travel  before  entering  the  different  houses. 
When  the  houses  are  situated  close  to  each  other,  the  difference 
must  be  very  considerable.  Some  apparatuses  of  this  kind  have 
no  box  attached  to  them,  and  work  directly  to  and  from  the  boiler. 
I  consider  the  box,  however,  as  a  very  important  appendage ; 
not  only  because  it  affords  greater  facility  for  working  the 
apparatus,  but  because  any  of  the  other  arrangements  may  be 
repaired  more  easily,  and  parts  may  even  be  taken  away  with- 
out in  the  least  affecting  the  working  of  the  rest. 

As  I  have  already  stated,  pipes,  in  reality,  radiate  a  very  dry 
heat ;  though  many  think  otherwise,  because  the  air  of  a  hot- 
18* 


208       VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL. 

house,  so  heated,  is  generally  less  arid  than  one  heated  by  a  hot- 
air  stove.  This  arises  from  the  fact,  that,  by  hot-water  pipes,  a 
much  larger  radiating  surface  is  presented  to  the  atmosphere  of 
the  house  than  by  any  other  method,  and  the  heat  is  radiated  at 
a  lower  temperature,  and  more  equally  diffused;  hence,  less 
moisture  is  carried  upwards  by  currents  of  heated  air  and 
deposited  on  the  glass  by  condensation.  Thus,  it  is  clear,  that 
the  larger  the  heating  surface  that  is  acted  upon  by  the  air,  and 
the  lower  the  temperature  of  that  surface,  the  less  moisture  will 
be  drawn  from  the  plants  and  the  atmosphere  of  the  house.  It 
is  always  desirable,  however,  to  provide  against  aridity  in  the 
atmosphere,  as  heated  air  will  have  its  supply  of  moisture,  come 
from  where  it  will ;  and  if  it  cannot  draw  it  from  anywhere  else, 
it  will  draw  it  from  the  plants,  or  whatever  can  supply  the  larg- 
est quantity  under  its  influence.  For  this  purpose,  a  number 
of  troughs  are  made  to  fit  on  the  pipes,  made  of  zinc  or  gal- 
vanized tin.  These  troughs  may  likewise  be  made  of  earthen 
ware,  and  perhaps  more  cheaply  than  of  zinc,  though  more  lia- 
ble to  be  broken.  They  may  be  filled  with  a  syphon  from  the 
pipes,  or  by  a  common  water-pot.  When  moisture  is  required 
in  the  house,  an  agreeable  evaporation  will  be  given  off,  and 
which  can  be  rendered  still  more  healthful,  by  putting  in  a  few 
bits  of  carbonate  of  ammonia  among  the  water,  or  common 
pigeon's  dung,  or  guano.  As  the  water  warms,  ammonia  will 
be  evolved  into  the  atmosphere  and  greedily  absorbed  by  the 
plants. 

In  recommending  this  system  to  the  notice  of  those  who  may 
be  entering  upon  the  erection  of  hot-houses,  we  would  state  that 
we  recommend  it  not  only  upon  our  own  experience,  but  also 
upon  that  of  others,  whom  we  consider  much  better  qualified 
to  decide  upon  its  merits.  Nor  do  we  mean  to  assert  that  it  is 
the  ne  plus  ultra  of  a  heating  apparatus,  although,  under  certain 
circumstances,  it  is  the  nearest  approach  to  it  that  has  yet  come 
under  our  observation.  In  making  this  statement,  we  do  not 
wish  to  dispute  the  judgment  of  those  who  think  differently,  and 
who  have  opposed  it  more  from  a  feeling  of  groundless  distrust, 
than  from  any  fact  they  can  bring  to  bear  against  it.  We  have 
conversed  with  many  who  would  prefer  heating  each  house  with 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.        209 

its  own  fire  and  boiler,  and  be  at  the  additional  trouble  of  attend- 
ing them  too.  This,  however,  springs  from  a  fear  entirely  with- 
out foundation,  and  we  are  convinced  that  a  little  experience  in 
the  working  of  this  double  system  of  heating  would  so  prove  it. 
It  is  a  very  singular  attachment  which  some  people  have  for  old 
methods  and  customs,  that  they  will  unflinchingly  adhere  to 
them,  however  little  merit  they  may  have  to  recommend  them. 
Some  individuals,  with  a  self-sufficiency  altogether  incompatible 
with  knowledge,  will  smile  or  sneer  at  what  they  are  pleased  to 
call  the  folly  of  enthusiasm,  and,  without  seeming  to  be  in  any 
way  sensible  of  the  importance  of  whatever  tends  to  the  im- 
provement of  horticulture,  regard  these  innovations  merely  as 
idle  speculations  of  men  who  have  nothing  else  to  do  but  invent 
them ;  and  while  we  cannot  guard  too  much  against  the  adoption 
of  methods  that  will  prove  inconvenient  in  practice,  although 
supported  by  theory,  it  is  an  injury  to  gardening,  as  an  art,  to 
give  an  unqualified  opposition  to  systems  that  have  proved  their 
superiority,  and  are  still  capable  of  great  improvement.  This 
plan  is  not  introduced  under  the  deceptive  cognomen  of  cheap- 
ness. Its  cost  will  very  much  depend  upon  the  circumstance  of 
position,  and  may,  after  all,  be  much  less  than  some  of  the  costly 
and  cumbrous  apparatuses  that  are  now  in  use.  The  easiness 
with  which  it  is  worked  adds  an  additional  item  to  its  worth, 
for,  when  once  set  agoing,  and  understood,  the  veriest  novice 
could  manage  it.  * 

*  It  is  the  common  fate  of  new  systems  connected  with  the  art  of 
horticulture,  that  they  are  eulogized  beyond  their  real  merits  by  their 
advocates,  and  decried  as  strongly  by  their  opponents  j  for  every  new 
system  has  always  both  friends  and  foes,  each  of  whom  are  unwilling  to 
adhere  to  the  naked  truth,  and  equally  incapable  of  appreciating  its 
merits  with  exactness.  When  a  person  invents,  or  fancies  he  has 
invented,  something  new,  he  is  too  much  inclined  to  set  a  high  value 
upon  it ;  for,  if  it  has  cost  him  much  labor,  he  is  unwilling  to  think  he 
has  been  diligent  in  vain.  He,  therefore,  magnifies  what  is  merely  an 
alteration  into  an  improvement,  and  probably  prevails  upon  the  imagi- 
nation of  others  to  fall  into  a  false  approbation  of  the  system,  and  to 
regard  that  as  a  valuable  desideratum  which,  at  the  best,  was  only  a 
novelty.  If  durability  and  econo'my  in  working  be  allowed  to  constitute 
any  part  of  excellence  in  a  system,  then  this  one  has  especial  claims  to 
our  notice  j  a  fact  which  cannot  be  said  of  many  others. 


210       VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL. 


Fig.  43. 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         211 

Fig.  43  shows  a  house  wherein  provision  is  made  for  increas- 
ing the  heating  surface,  when  more  than  a  very  moderate  degree 
of  heat  is  required  from  the  pipes.  A  box  or  tank,  made  of  wood 
or  zinc,  is  placed  under  the  stage,  and  passes  all  round  it  on  a 
level  with  the  pipes.  This  tank  is  supplied  by  a  branch  pipe  <z, 
proceeding  from  the  flow-pipe,  and  is  provided  with  a  tap  at  3,  for 
shutting  off  and  on  the  water  when  necessary.  This  is  a  most 
convenient  arrangement ;  for,  if  a  moderate  heat  only  be  required 
from  the  apparatus,  then  the  pipes  will  be  sufficient,  and  a  very 
small  fire  will  be  required  to  heat  them,  as  the  quantity  of  water 
is  small.  When  it  is  found  necessary  to  increase  the  tempera- 
ture of  the  house,  the  pipes  being  then  tolerably  warm,  the 
water  from  the  flow-pipe  is  admitted  into  the  tank  by  opening 
the  tap.  The  heat  of  the  pipes  is  slightly  reduced,,  but  the 
radiating  surface  is  increased,  and  the  temperature  of  the  house 
rises  by  an  equal  distribution  of  heat.  It  might  be  supposed 
that  a  quantity  of  specific  heat  is  lost  to  the  atmosphere,  by 
drawing  it  from  the  pipes  and  throwing  it  into  a  body  of  cold 
water.  Not  so,  however,  as  a  little  consideration  will  make 
sufficiently  clear.  Thus,  if  the  atmosphere  of  the  house  be  at 
45  degrees,  the  water  in  the  tank  will  be  at  45  degrees  also. 
Now,  suppose  the  tank  and  the  pipes  to  contain  equal  bodies  of 
water,  then,  if  the  pipes  communicate  a  portion  of  their  heat  to 
the  tank,  the  temperature  of  the  water  in  the  tank  will  rise  just 
as  much  as  the  water  in  the  pipes  will  fall ;  for,  if  two  equal 
bodies  of  water,  at  different  temperatures,  are  mingled  together, 
the  temperature  produced  by  the  mixture  will  be  the  mean  of 
their  previous  temperature.  Suppose,  for  instance,  that  the 
temperature  of  the  water  in  the  pipes  was  300,  and  that  in  the 
tank  45  degrees,  and  that,  by  the  opening  of  the  tap,  the  hot 
water  in  the  pipes,  and  the  cold  water  in  the  tank,  were  inti- 
mately mingled  together,  then  the  temperature  of  both  would 
be  122-5  degrees.  The  temperature  of  both  has  been  equal- 
ized, but  the  atmosphere  of  the  house  has  lost  none  by  the 
change,  but  rather  gained,  as  the  tank  being  77  degrees 
above  the  temperature  of  the  atmosphere,  more  heat  will  be 
diffused  than  with  the  pipes  alone  at  double  the  temperature, 
and  the  object  will  be  gained,  namely,  that  of  preventing  the 


212        VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL. 

plants  from  being  subjected  to  a  high  temperature,  that  are  situ- 
ated in  the  vicinity  of  the  pipes.  In  the  drawing,  (Fig.  43,) 
the  flow  and  return  pipes  are  placed  together,  the  other  side 
being  heated  by  the  flue  from  the  fire.  This  arrangement  is 
intended  to  economize  heat,  and  to  save  the  expense  of  pipes, 
which,  in  some  places,  might  be  an  object  of  importance,  and 
even  if  they  were  not  so,  the  plan  is  decidedly  good.  As  for  the 
tank,  it  is  an  admirable  contrivance.  Not  only  is  the  evil  of 
having  highly  heated  pipes  for  weeks  and  months  together, 
directly  under  the  roots  of  plants,  prevented,  but  when  the  tank 
is  once  heated,  a  more  agreeable  and  healthy  warmth  will  be 
produced,  and  the  equilibrium  of  temperature  be  maintained 
for  a  much  longer  time. 

The  tanks  used  may  either  be  wooden  or  metallic.  The  lat- 
ter are  preferable,  both  on  account  of  durability  and  radiation 
of  heat,  although  wooden  ones  are  much  cheaper,  and  answer 
the  purpose  perfectly.  Wooden  tanks,  if  the  wood  be  kyanized, 
or  otherwise  treated  with  a  metallic  solution,  will  last  for  many 
years,  and  produce  a  very  agreeable  warmth.  Galvanized  iron 
and  zinc  are  now  in  common  use  for  this  purpose.  The  dura- 
bility imparted  to  it  by  the  process  of  galvanization,  which  pre- 
vents oxidation,  is  evident  from  the  number  of  articles  made 
of  this  material  and  exposed  to  the  atmosphere.  For  horticul- 
tural purposes,  this  article  is  likely  to  become  exceedingly 
useful ;  as  every  one  is  aware  of  the  injury  which  ordinary  hot- 
water  pipes,  and  other  metallic  substances  used  in  horticultural 
erections,  are  liable  to  from  rast.  Tanks  made  of  this  material 
give  out  their  heat  much  more  rapidly.  But  it  must  be  consid- 
ered that  the  same  circumstances  that  would  render  them  more 
quickly  effectual,  would  also  render  their  effect  more  transient. 
For  pits  and  very  small  houses,  the  pipes  and  tanks  might  be 
made  of  this  material.  Its  cheapness  and  lightness  are  impor- 
tant advantages  in  its  favor;  for,  when  heavy-cast  metal  pipes 
are  conveyed  to  a  great  distance,  the  cost  of  carriage  will  nearly 
amount  to  the  same  sum  as  would  purchase  galvanized  iron  or 
zinc  tanks,  and  convey  them  too. 

In  using  this  kind  of  tanks,  the  utmost  care  ought  to  be 
taken  in  supplying  them  with  water.  They  ought  never  to  be 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         213 

over  one  third  or  half  full ;  the  less  water  that  is  in  them  the 
better,  compatible  with  safety.  To  work  well,  the  water  ought 
never  to  boil  into  them,  otherwise  the  force  of  the  steam  will 
expand  the  metal,  and,  if  the  heat  continue,  it  is  liable  to  burst. 
Fig.  44  represents  a  house  heated  with  a  tank  made  of  galvan- 
ized zinc.  Next  to  the  boiler  there  is  a  short  piece  of  cast-iron 
pipe  which  prevents  the  zinc  from  being  affected  by  the  imme- 
diate action  of  the  fire.  The  house  from  which  this  sketch  was 
taken  has  been  in  use  for  some  years,  and  has  given  perfect  sat- 
isfaction, while  the  original  cost  was  very  small.  The  principal 
objection  to  the  use  of  this  material  for  heating  purposes,  is,  as 
I  have  already  stated,  the  rapidity  with  which  it  is  heated,  and 
the  rapidity  with  which  it  parts  again  with  its  heat.  This  cir- 
cumstance renders  it  a  good  conductor,  but  a  bad  retainer,  of 
heat;  useful  where  speedy  and  immediate  action  is  required,  but 
useless  where  a  slow  and  long-continued  radiation  is  necessary 
at  a  very  low  temperature,  as,  for  instance,  for  bottom-heat, 
for  propagating-beds,  and  for  plant-stoves.  In  such  circum- 
stances, we  should  decidedly  prefer  wood,  particularly  for  the 
first-mentioned  purposes.  In  green-houses,  and  even  in  forcing- 
houses,  it  may  answer  well ;  for  it  must  be  admitted  that  the 
source  of  heat  must  ever  be  looked  for  at  the  boiler,  not  in  the 
material  of  which  the  tanks  or  pipes  are  made.  And,  although 
the  advantage  of  employing  a  material  that  will  absorb  the  heat 
given  off  from  the  source  to  any  extent,  and  part  with  it  gradu- 
ally, must  be  apparent,  at  least,  when  it  is  an  object  to  take 
advantage  of  the  heat  so  absorbed,  store  it  up,  so  to  speak,  with 
the  view  of  employing  it  when  the  action  of  the  apparatus 
becomes  enfeebled.  The  law  by  which  this  is  effected  is  the 
same  as  that  by  which  the  two  bodies  of  water  become  equal- 
ized in  temperature  by  admixture  as  described  on  page  210. 
This  is  the  law  of  equalization,  which  constantly  tends  to  bring 
all  bodies  to  an  equal  temperature.  If,  for  instance,  the  hot  water 
from  a  boiler  be  admitted  into  two  separate  tanks,  one  of  wood 
and  the  other  of  zinc,  then,  by  placing  the  palrn  of  the  hand  upon 
the  wooden  tank,  it  will  feel  agreeably  warm,  while  the  zinc  01 
tin  one  would  be  quite  unbearable,  if  not  burn,  and  this  while 
the  temperature  of  the  water  in  both  tanks  was  the  same.  The 


214       VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 


Fig.  44. 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.        215 

reason  is,  the  metal  is  a  good  conductor,  and  quickly  conveys 
away  the  heat  from  the  water  by  imparting  it  to  a  colder  body, 
while  the  wood  is  a  bad  conductor,  and  retains  it.  Again,  the 
metallic  tank  will  have  the  same  temperature  as  the  water 
within,  before  the  wooden  one  is  sensibly  warm.  In  fact,  the 
wooden  tank  retains  and  accumulates  the  heat,  while  the  metal- 
lic one  gives  it  off  as  soon  as  it  receives  it.  None  of  this  heat, 
however,  is  lost  to  the  atmosphere  of  the  house ;  for  though  the 
wooden  tank  parts  with  its  accumulated  heat  more  slowly,  it  as 
certainly  parts  with  it,  in  the  course  of  time,  as  the  metallic  one. 
It  parts  with  its  heat  gradually  till  it  is  reduced  to  the  same 
temperature  as  the  atmosphere  around  it.  A  house  heated  with 
a  wooden  tank  will  maintain  an  average  temperature  with  less 
expenditure  of  fuel  than  a  thin  metallic  one,  the  other  circum- 
stances being  equal,  which  is  accounted  for  by  the  fact  that 
when  a  house  is  suddenly  heated,  the  wann  air  is  forced  rapidly 
upward,  and,  coming  in  contact  with  the  glass,  is  rapidly  cooled, 
descends,  and  is  again  warmed,  till  the  warming  surface  is 
entirely  deprived  of  its  heat ;  then  the  temperature  falls.  On 
the  other  hand,  when  the  heat  is  disseminated  at  a  low  temper- 
ature, the  atmosphere  is  less  agitated,  and  the  ascending  air 
less  rapid  in  its  motion.  Not  so  much  escapes  through  the  laps 
of  the  glass,  or  is  cooled  down  by  the  external  cold  upon  its 
surface ;  and  hence,  the  same  quantity  of  specific  heat  maintains 
a  given  temperature  for  a  longer  time,  when  gradually  given  off, 
than  when  suddenly  given  off  at  a  high  temperature. 

Although  the  sudden  rise  and  fall  of  temperature  by  thin 
metallic  tanks  be  apparent,  we  do  not  condemn  their  use  for  all 
purposes.  As  we  have  already  said,  they  may  be  profitably 
used  in  many  kinds  of  erections,  and  for  various  purposes ;  and 
I  consider  them  worthy  of  more  extended  trials.  But  I  do  not 
believe  that  they  will  ever  supersede  cast  metal  pipes  for  the 
general  purposes  of  heating  by  hot  water ;  and  for  a  retention- 
tank,  I  would  decidedly  prefer  wood.  Fig.  45  represents  a 
house  with  a  wooden  tank,  in  which  the  water  circulates  by 
various  divisions,  after  it  enters  from  the  flow-pipe.  This  tank 
was  erected  in  a  plant-house  beneath  the  stage,  as  shown  in  the 
end  section,  Fig.  46,  which  may  be  objectionable  as  regards 


Fig.  45. 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.        217 

its  position,  but  the  chief  object  was  to  hold  and  retain  a  sup- 
ply of  warm  water,  which  it  did  admirably,  and  effectually 
warmed  the  house  besides.  The  manner  in  which  this  tank 
retained  the  heat  after  the  fire  had  ceased  to  burn,  impressed 
me  with  the  idea  that  heat  could  be  drawn  off  from  the  regular 
apparatus,  and  applied  afterwards  when  necessary,  or  for  any 
other  purpose.  I  believe  the  heat  generated  by  wooden  tanks  to 
be  most  favorable  to  the  structural  development  of  plants,  as  con- 
taining more  moisture  than  heat  radiated  from  either  iron  or 
brick,  because  the  temperature  is  lower. 

We  have  already  remarked  that  the  tank  system  of  heating 
hot-houses  has  but  very  lately  been  brought  into  general  notice, 
and  still  receives  much  less  attention  than  its  utility,  simplicity, 
and  economy  claim  for  it ;  and  where  it  has  been  used,  it  is 
chiefly  as  a  medium  of  bottom-heat,  for  which  it  is  undoubtedly 
superior  to  anything  that  has  yet  been  applied.  The  efficiency 
of  tanks  in  supplying  atmospheric  heat  has  been  doubted  by 
some  and  denied  by  others,  without,  however,  as  far  as  I  can 
learn,  bringing  any  practical  facts  to  bear  upon  the  subject.  I 
am  convinced  that  the  system,  rightly  applied,  will  prove  the 
doubts  to  be  entirely  without  foundation.  Simplicity  in  any 
system  of  heating  is  a  point  of  incalculable  importance ;  and 
when  economy  and  adaptibility  are  combined  with  it,  a  claim  is 
presented  which  facts  only  can  overthrow.  It  is  very  true  that 
we  practicals  are,  many  of  us  at  least,  prone  to  adhere  bigotedly 
to  any  method  with  which  we  are  acquainted,  and  which  we 
have  already  proved  safe  and  simple,  and  are  unwilling  to 
believe  that  any  other  method  can  be  safer  and  simpler  than 
itself.  Gardeners  are  proverbially  a  cautious  and  thoughtful 
class  of  men;  perhaps  seldom  directly  opposing  principles 
founded  upon  theoretical  deductions,  but  frequently  slow  in 
instituting  experiments  with  the  view  of  establishing  their  truth. 
In  these  days  of  invention  and  progress,  it  is  the  duty  of  every 
one  engaged  in  horticultural  pursuits,  and  particularly  garden- 
ers, not  only  to  make  themselves  acquainted  with  the  views  and 
opinions  of  other  persons,  but  to  test,  by  various  counter-experi- 
ments, the  conclusions  they  have  drawn.  No  man  is  justified 


218    VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

in  regarding  his  knowledge  of  any  system  well-founded,  except 
upon  experiments  and  observations  of  his  own. 

Gardeners  are,  of  all  others,  the  best  qualified  to  decide  upon 
the  merits  of  any  system  of  heating  hot-houses,  and  to  ascertain 
its  effects  upon  vegetable  life.  They  are,  by  necessity,  familiar 
with  the  habits  of  plants ;  and,  by  an  instinctive  practical  knowl- 
edge, (if  nothing  more,)  they  are  less  likely  to  be  deceived  by 
the  peculiarities  produced  by  heat  and  cold,  dryness  and  moist- 
ure, either  in  deficiency  or  in  excess.  The  gardener  is  able  to  tell 
whether  his  plants  be  in  vigorous  health,  or  the  reverse  ;  whether 
they  are  suffering  from  atmospheric  impurity,  aridity,  or  stagna- 
tion ;  and,  besides,  the  necessities  of  culture  compel  him  to 
study  the  causes  of  such  changes  and  conditions.  All  gardeners 
are  aware  that  causes  the  most  dissimilar  will  produce  results  in 
every  way  identical,  while  the  self-same  causes,  repeated  with 
the  greatest  care,  and  under  circumstances  where  it  was  appar- 
ently impossible  for  them  to  be  at  variance  with  the  first,  will 
nevertheless  produce  results  totally  different ;  and  the  universal 
axiom,  that  like  causes  produce  like  results,  would  sometimes 
appear  to  be  set  at  naught. 

It  has  ever  been  a  desideratum,  as  regards  the  heating  appa- 
ratus, especially  the  hot-water  kind,  that  there  should  be  among 
gardeners  a  perfect  knowledge  of  their  details,  and  of  the  man- 
ner of  repairing  them.  It  is  true  we  know  when  they  become 
warm,  and  when  they  cool ;  but,  as  for  the  rest,  once  erected  and 
the  workmen  gone,  they  are  like  a  watch,  or  a  doctor's  prescrip- 
tion, —  they  may  go  wrong,  and  become  unworkable,  but  we 
cannot  put  them  right,  nor  scarcely  discover  what  is  the  matter 
with  them,  till  we  send  for  the  tradesman;  and  then,  after  an 
hour  or  two  pulling  and  hammering,  dusting  and  besmearing  our 
plants,  turning  everything  in  the  house  topsy-turvy,  lo !  we  are 
told  that  a  joint  had  cracked,  a  collar  had  split,  or  some  such 
mishap  had  befallen  our  apparatus.  Facts  of  this  kind  will  be 
in  the  experience  of  every  one  who  has  had  much  to  do  with 
heating  apparatus.  Now  what  I  would  urge  is,  that  no  part  of 
a  heating  apparatus  should  be  under  ground,  or  buried  in  brick- 
work so  far  as  it  is  concerned  with  the  interior  of  the  house. 
Not.  an  inch  of  it  ought  to  be  covered  up  with  anything.  It 


VARIOUS   METHODS   OF    HEATING   DESCRIBED   IN    DETAIL.    219 

ought  to  be  all  exposed,  as  far  as  possible,  and  of  easy  access. 
Moreover,  let  it  be  simple  in  its  arrangements ;  the  simplicity 
of  any  system  is  a  plea  in  its  favor.  Some  people,  however, 
despise  simplicity,  and  would  baptize  everything  about  them  with 
confusion  and  complexity.  We  have  met  with  people  who  fancy 
that  their  green-house  could  not  be  heated  without  an  array  of 
pipes,  winding  here  and  there,  as  intricately  arranged  as  the 
wheels  of  a  watch,  and  as  useless  for  the  heating  of  their  house 
as  the  pillars  that  support  the  portico  of  their  dwelling.  One 
would  think  that  they  admired  cast  metal  pipes  more  than  their 
flowering  plants. 

One  of  the  chief  commendations  of  hot  water,  as  a  heating 
power,  is  the  facility  with  which  you  can  bring  it  in  contact 
with  the  atmosphere  of  the  house  ;  however  simple  the  manner 
in  which  it  may  be  applied,  it  is  not  the  less  effectual ;  and  how- 
ever commendable  in  other  respects  the  warming  of  hot-houses 
by  improved  methods  of  hot  air  may  be,  the  channels  and 
chambers,  the  numerous  hot  and  cold  air  drains,  the  under- 
ground building  of  brick-work,  and  the  multifarious  intricacies 
of  its  arrangements,  are  sufficient  to  deter  any  person  from  the 
erection  of  such  a  complicated  affair.  This  will  be  apparent 
from  a  glance  of  the  drawing  of  Meek's  improved  method  of  a 
hot-air  heating-apparatus,  given  on  page  197.  Such  a  concern 
may  do  very  well  on  paper,  but  it  will  not  do  in  practice.  It 
may  answer  admirably  as  a  plaything  for  amateurs,  who  have  a 
fancy  for  it,  and  nothing  else  to  do  with  their  time  but  to  amuse 
themselves  with  the  motions  of  air ;  but,  as  a  method  of  warm- 
ing a  hot-house,  no  sane  person  will  adopt  it,  when  he  can  have 
the  thing  done  by  a  simple  tank  and  boiler  at  half  the  expense. 
As  a  system,  it  is  good  for  naught.  No  person  who  understands 
it  will  adopt  it ;  and  those  who  do  not  know  it,  but  will  have  it, 
let  them  try. 

The  tank  system  may  justly  be  regarded  a  real  improvement 
in  heating,  whether  for  top  or  bottom ;  and  it  is  the  simplest, 
and  perhaps  the  cheapest,  that  has  yet  been  brought  under  pub- 
lic notice.  The  sketches  we  have  given  are  probably  not  the  best 
that  could  be  adopted.  It  is  yet  open  to  great  improvement,  and 
it  would  be  premature,  at  present,  to  hazard  an  opinion  upon 
19* 


220  VARIOUS    METHODS    OF   HEATING    DESCRIBED   IN    DETAIL. 

what  may  hereafter  be  effected  by  it,  by  the  friction  of  one  idea 
against  another  in  the  course  of  experience.  For  small  pits, 
filled  with  young  stock,  it  is  invaluable,  as  a  pipe  may  be  car- 
ried from  a  boiler,  heating  other  structures,  into  a  pit  near  by ; 
and,  these  being  easily  covered  at  night,  a  sufficiency  of  heat 
may  thus  be  conducted  into  them  to  keep  the  plants  safe 
during  the  winter,  without  much  increase  of  fuel,  or  any  with- 
drawal of  heat  from  the  structure  for  which  the  apparatus  was 
originally  constructed.  Green-houses  are  generally  too  much 
crowded  in  winter,  and  the  adoption  of  dry  pits  for  the  conserva- 
tion of  plants  that  are  somewhat  hardy  in  their  nature,  is  riot 
so  common  as  it  ought  to  be.  Pits  might  be  so  arranged 
as  to  obtain  the  superfluous  heating  power  from  other  houses. 
This,  in  some  instances,  has  been  done,  and  it  is  likely  that 
more  will  ere  long  be  done  in  the  same  way ;  for  if  the  vast 
amount  of  fuel,  consumed  by  the  general  methods  of  heating, 
could  be  economically  applied,  without  waste,  it  is  not  exaggera- 
tion to  say  that  at  least  one  third  could  be  saved. 

The  hygrometrical  and  ammoniacal  condition  of  the  atmos- 
phere of  hot-houses  has  not  received  that  attention,  in  connec- 
tion with  heating,  which  the  importance  of  the  matter  evidently 
demands.  We  have  books  enough  teaching  us  the  effects  of 
certain  volatile  and  subtile  fluids  upon  vegetable  life,  and  exhib- 
iting a  multitude  of  facts  which  no  person  will  venture  to  dis- 
pute ;  yet,  in  this  matter,  we  practicals  have,  in  a  great  measure, 
been  deaf  to  the  teachings  of  science,  and  blind  to  the  lessons 
of  nature.  Practically,  or  experimentally,  we  have  made  but 
little  inquiry  whether  invigorating  or  contaminating  gases 
abounded  in  our  hot-houses.  Now,  nature  is  either  a  good  or 
a  bad  teacher,  just  in  proportion  as  our  knowledge  of  her  im- 
mutable laws  is  limited  or  comprehensive.  When  we  confine 
plants  in  a  case  of  glass,  as  in  a  green-house,  if  we  give  them 
soil  to  grow  in  and  water  to  drink,  we  are  apt  to  think  they 
ought  to  be  contented ;  and  if  they  do  not  thrive  well  and  prove 
productive,  we  call  them  ungrateful,  or  very  difficult  to  rear. 
Now,  we  ought  to  consider  that  plants  feed  by  their  leaves  as 
well  as  by  their  roots,  and  that  the  volume  of  air  in  which  the 
leaves  are  expanded,  requires  to  be  as  regularly  moistened  and 


VARIOUS   METHODS    OF    HEATING   DESCRIBED   IN    DETAIL.    221 

manured,  as  the  body  of  earth  in  which  they  grow.  It  may 
appear  vague  and  visionary  to  talk  of  manuring  the  atmosphere 
of  a  hot-house,  but  the  thing  is  in  reality  neither  so  vague  nor 
yet  so  visionary  as  it  seems ;  for  here  science  comes  to  our 
aid,  and  not  only  defines  the  vagueness,  but  converts  the  vision 
into  a  practical  reality.  It  proves  to  us,  both  the  benefits  of 
manuring  the  air,  and  the  manner  of  doing  it.  We  know  that 
plants  derive  a  large  portion  of  their  food  from  the  atmosphere  ; 
and  we  know,  also,  that  the  arid  atmosphere  of  a  hot-house  is  not 
always  charged  to  a  proper  degree  with  these  life-giving  gases. 
An  impoverished  atmosphere  must  have  the  same  effect  as  an 
impoverished  soil.  This  is  a  well-known  fact,  and  requires  no 
demonstration  to  prove  it.  We  are  well  aware  that  many 
plants  will  grow  luxuriantly  for  years,  suspended  in  the  air,  pro- 
viding they  be  kept  in  a  condition  calculated  to  sustain  them ; 
but  deprive  them  of  these  gases,  and  they  will  die,  —  deprive 
the  atmosphere  of  its  humidity,  and  they  will  quickly  cease  to 
exist  as  living  plants.  These  vegetables  absorb  carbonic  acid, 
ammonia,  and  water,  from  the  atmosphere,  by  their  leaves,  even 
more  abundantly  than  by  their  roots.  This  is  especially  the 
case  with  plants  cultivated  in  pots  ;  their  roots  being  circum- 
scribed into  a  small  space,  the  nourishment  is  speedily  exhausted, 
and  if  the  atmosphere  be  at  the  same  time  robbed  of  its  gaseous 
elements  by  artificial  heat,  the  plants  must  perish,  if  this  defi- 
ciency is  not  supplied  to  them  by  artificial  means. 

We  have  seen,  that  plants,  even  of  a  ligneous  nature,  will 
grow,  form  lignin,  and  proteine  compounds,  while  suspended  in 
a  moist  warm  atmosphere,  much  in  the  same  manner  as  plants 
do  when  growing  in  the  soil.  The  amount  of  mineral  matter 
they  contain  is  indeed  very  small,  and  may  be  derived  from  the 
dust  continually  floating  in  the  atmosphere,  which  is  dissolved 
as  it  falls  upon  the  leaves,  and  is  absorbed  with  the  atmospheric 
fluids.  Here,  then,  we  have  plants  subsisting  upon  the  ingre- 
dients of  the  atmosphere  ;  and  experiments  seem  to  prove  that 
all  plants  are  nourished  by  the  same  substances,  in  variable 
proportions,  the  chief  of  which  are  carbonic  acid,  water,  and 
ammonia. 

Experience  has  already  proved  the  beneficial  effects  of  these 
substances  as  fertilizers,  not  only  of  the  soil,  but  also  of  the 


222    VARIOUS   METHODS    OF    HEATING    DESCRIBED    IN    DETAIL. 

atmosphere.  Plants  watered  with  a  weak  solution  of  the  salts 
of  ammonia  (smelling  salts)  will,  in  a  few  days,  show  their 
invigorating  effects  ;  and  plants  grown  in  a  hot-house,  with 
the  atmosphere  impregnated  with  ammonia,  will  exhibit,  in 
a  manner  equally  as  striking,  its  beneficial  influence.  Every 
gardener  is  aware  that  plants,  growing  in  frames  or  pits 
heated  with  fermenting  manufe,  will,  under  ordinary  circum- 
stances, evince  a  much  greater  degree  of  luxuriance  than  in 
any  other  situation.  In  fact,  dung-beds  are  considered  an  an- 
tidote for  nearly  every  disease  that  plants  are  heir  to,  and  not 
without  a  well-grounded  knowledge  of  their  effects  ;  and 
hence,  when  a  gardener  wishes  to  invigorate  sickly  plants,  he 
straightway  plunges  them  into  a  hot-bed,  and  if  there  be  any 
vitality  left  in  the  plant,  it  seldom  fails  in  pushing  out  vigorous- 
ly. Now  nothing  is  more  obvious  than  the  fact  that  neither  the 
heat,  nor  the  moisture  alone,  produced  this  result ;  for  if  the 
plant  had  been  plunged  in  a  hot-bed  warmed  with  the  combus- 
tion of  fuel,  in  nine  cases  out  of  ten  the  result  would  have  been 
the  very  reverse.  In  fact,  it  is  found,  by  long  experience,  that 
neither  heat  nor  moisture  alone  will  compensate  for  the  removal 
of  a  sickly  plant  from  the  congenial  warmth  of  a  well-prepared 
dung-bed.  Now,  the  question  which  presents  itself  for  solution, 
in  regard  to  this  mode  of  heating,  is,  What  is  the  cause  of  this 
difference,  and  how  can  it  be  otherwise  produced  ?  If  we  con- 
sider the  effects  due  to  the  gases  already  mentioned,  to  be  fully 
established,  we  will  find  that  the  secret  of  all  this  lies  in  the 
stimulating  gases  of  the  manure,  which  constantly  surround  the 
plants  when  exposed  to  the  mild  heat  of  a  dung-bed.  The  old, 
and  now  almost  obsolete,  plan  of  warming  forcing-houses  with 
accumulated  masses  of  fermenting  manure,  is  well  known ;  and 
the  luxuriance  of  vines,  forced  by  this  method,  is  as  well  known 
as  the  method  itself.  This  luxuriance  was  produced  by  the 
ammoniacal  and  other  gases  evolved  during  the  process  of  fer- 
mentation ;  and  though  this  method  of  forcing  has  been  entirely 
laid  aside,  on  account  of  its  unsightly  appearance,  and  the  incon- 
venience of  keeping  up  a  constant  supply  of  well-prepared  ma- 
nure, still  the  merits  it  possessed,  by  its  ammoniacal  properties, 
have  not  yet  been  secured  in  any  other  mode  of  heating. 


VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.    223 

Suppose,  then,  that  we  have  already  solved  the  first  part  of 
the  problem,  by  attributing  these  results  to  the  beneficial  action 
of  gases  arising  from  fermenting  manure  ;  let  us  consider  how 
we  can  produce  those  gases,  under  other  circumstances,  i. «.,  with- 
out the  presence  of  manure. 

Ammonia  is  the  result  of  a  combination  of  the  two  gases, 
hydrogen  and  nitrogen,  and  has  been  hitherto  known  to  gar- 
deners, and  applied  by  them,  chiefly  in  the  state  in  which  it 
exists,  and  is  produced  by  the  decomposition  of  animal  and  veg- 
etable matter,  as  in  the  formation  of  dung-beds,  from  which  we 
can  perceive  it  escaping  in  an  uncombined  state  into  the  atmos- 
phere. It  is  easily  distinguished  from  all  other  gases  by  its 
powerful,  penetrating  odor.  It  remains,  however,  but  a  short 
time  in  this  state,  as  it  is  speedily  absorbed  by  porous  sub- 
stances, and  by  living  plants,  and  combines  with  other  gases, 
forming  compounds ;  with  carbonic  acid,  for  instance,  forming 
the  carbonate  of  ammonia  of  the  shops,  from  which  it  can  read- 
ily be  disengaged  and  evolved  into  the  atmosphere  of  a  hot-house. 
Ammonia,  in  the  state  of  a  carbonate,  is  exceedingly  volatile,  and 
when  a  small  portion  is  mixed  with  water,  arid  the  temperature 
raised  to  about  112  degrees,  a  large  quantity  of  ammonia  is 
evolved.  This  will  be  still  better  effected  by  mixing  a  small 
quantity  of  potash,  soda,  or  lime,  with  the  water  in  which  the 
ammonia  has  been  absorbed.  The  salt  which  held  the  ammo- 
nia in  combination  is  taken  up  by  these  alkalies,  and  the  ammo- 
nia, being  exceedingly  volatile,  escapes  into  the  atmosphere. 

By  dissolving  the  sulphate  or  carbonate  of  ammonia  in  hot- 
water  tanks,  or  in  thin  troughs  placed  over  the  pipes  and  flues, 
an  atmosphere  may  be  produced  strikingly  similar  to  that  of  a 
dung-bed,  and  capable  of  producing  nearly  similar  effects. 
Dung-beds  are  probably  the  most  natural  methods  of  applying 
artificial  heat  to  plants ;  and  it  is  yet  doubtful  if  we  shall  ever 
be  able  to  supersede  them  in  their  invigorating  influence, 
although  much  may  be  done  to  modify  the  existing  evils  of  arid 
and  unwholesome  atmosphere  in  hot-houses.  The  mixture  of 
guano,  pigeon's  dung,  and  various  other  substances,  gives  off 
large  quantities  of  ammonia  in  warm  water,  and  may  be  used 
with  advantage  instead  of  its  salts.  Tanks  afford  an  excellent 


224     VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

means  of  effecting  this  purpose,  and  are,  not  only  on  the  score 
of  simplicity  and  economy,  but,  also,  in  an  ammoniacal  and 
hygrometrical  point  of  view,  the  best  methods  of  producing  heat 
with  which  I  am  acquainted. 

The  principal  kind  of  structures  to  which  the  tank  system  of 
heating  has  yet  been  applied,  to  any  extent,  in  England,  are 
what  are  termed  forcing-pits ;  and  in  these  it  has  been  exten- 
sively used,  with  much  success.  In  this  department  of  forcing, 
it  has  proved  one  of  the  greatest  improvements  of  modern  times. 
In  England  it  is  used  on  a  large  scale,  in  the  culture  of  pines, 
vines,  melons,  cucumbers,  &c.,  during  winter ;  and,  although 
in  this  point  of  view,  it  may  not  be  deemed  of  equal  importance 
in  this  country,  where  early  forced  fruits  and  vegetables  are  less 
demanded,  it  is,  nevertheless,  calculated  to  be  of  immense  value 
to  horticulturists  in  general,  and  plant-growers  in  particular. 
There  is  little  doubt,  but,  ere  long,  an  increasing  demand  for 
early  forced  fruits  and  vegetables,  fresh  from  the  forcing-house, 
will  stimulate  enterprising  individuals  to  the  erection  of  those 
cheap  and  simple  structures,  which  could  scarcely  fail  of  being 
a  profitable  investment.  A  given  space,  covered  with  a  glass 
roof,  and  otherwise  protected,  requires  a  comparatively  small 
amount  of  fuel  to  maintain  a  tolerable  degree  of  warmth  in  the 
soil,  much  less  than  is  generally  supposed.  It  is  not  my  pur- 
pose to  enter,  at  present,  into  the  details  of  this  question,  and  I 
merely  notice  it  in  connection  with  the  subject  of  heating.  By 
many  it  may  be  regarded  as  a  mere  speculative  theory,  which 
it  certainly  is,  yet  I  think  it  worthy  of  more  serious  considera- 
tion. 

In  many  of  the  English  nurseries,  tanks  are  used  for  stimu- 
lating the  growth  of  their  young  stock,  and  in  many  kinds  the 
annual  growths  are  indeed  remarkable.  We  have  seen  camellias, 
one  year  from  the  graft,  as  strong  and  vigorous  as  plants  three 
or  four  years  old  under  the  old  method  of  culture.  Almost  all 
kinds  of  green-house  plants  are  benefited  by  being  kept  in  tank 
pits,  and  we  are  inclined  to  think,  if  tank  pits  were  more  gener- 
ally used  by  the  nursery-men  of  this  country,  they  would  have 
their  plants  easier  got  ready  for  market,  and  they  would  require 
much  less  time  to  do  so  than  is  generally  the  case. 


VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.    225 

For  amateurs  wishing-  to  "try  to  grow  many  things,"  but 
who  have  little  time  or  money  to  spare  for  such  purposes,  one 
of  these  pits  is  just  the  thing  he  requires.  A  small  pit,  of  this 
nature,  with  a  very  little  attention,  would  keep  a  considerable 
number  of  green-house  plants  over  the  winter,  and  enable  him 
to  preserve  a  plentiful  stock  of  bedding-out  plants,  such  as  ver- 
benas, petunias,  calceolarias,  heliotropiums,  peristemons,  and 
many  other  pretty  little  things  for  the  decoration  of  the  flower- 
garden  in  summer.  How  much  more  pleasant  and  profitable 
would  it  be,  for  lovers  of  flowers,  to  have  a  little  pit  erected  in 
some  snug  corner  of  their  garden,  instead  of  losing  all  their 
roses  in  winter,  and  storing  their  drawing-room  plants,  —  their 
oranges,  their  camellias,  their  gardenias,  oleanders,  &c.,  —  into 
the  cellar,  from  which,  of  necessity,  they  are  frequently  taken 
half  dead.  Such  a  pit  as  I  allude  to  may,  or  may  not,  be  made 
to  comprehend  a  narrow  pathway  along  the  back,  —  this  would 
certainly  be  the  most  convenient,  —  and  this  portion  might  be 
covered  with  boards  or  shingles.  This  path  would  greatly  facil- 
itate the  operations  of  watering,  &c.  Whether  such  a  pit  ought 
to  be  sunk  below  the  ground,  or  placed  on  a  level  with  its 
surface,  will  depend  altogether  upon  the  nature  of  the  situation. 
Thus,  if  the  position  be  a  dry  one,  or  admits  of  being  made  so 
by  drainage,  it  should,  by  all  means,  be  sunk  two  or  three  feet 
below  the  surface.  But  if  the  situation  be  very  damp,  it  would 
certainly  be  bad  policy  to  sink  it  so  much  ;  for  whatever  advan- 
tage it  would  gain  in  the  way  of  protection,  would  be  more  than 
counterbalanced  by  the  dampness  which  would  be  unavoidable. 
A  pit,  sunk  in  a  dry  situation,  requires  less  fuel,  even  in  the 
severest  winters,  than  people  generally  suppose  ;  and  if  covered 
from  the  frost,  and  kept  dry,  many  plants  will  live  over  winter 
without  fire  at  all.  Plants  are  very  much  like  animals,  in  re- 
gard to  warmth;  when  once  accustomed  to  a  high  temperature, 
they  must  have  it  continually ;  but  inure  them  to  the  cold  of 
autumn,  and  they  will  do  with  less  heat  in  winter.  This  is 
not  saying  that  we  can  change  the  nature  of  plants,,  and  make 
them  to  endure  a  lower  temperature  than  they  can  possibly, 
under  any  circumstances,  bear.  But  we  know  that  plants  may 
be  brought  into  a  condition  to  enable  them  to  survive  a  much 


226    VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

greater  amount  of  cold  than  they  could  otherwise  have  endured, 
and  this,  too,  apart  from  the  application  of  artificial  heat.  When 
half-hardy  plants  are  destroyed  by  frost,  its  effects  are  most 
frequently  visible  at  the  collar,  or  lower  part  of  the  stem,  arising 
from  the  intense  action  of  the  cold  at  the  surface  of  the  ground, 
which,  in  combination  with  moisture,  first  contracts  and  then 
expands  the  principal  sap-vessels  of  the  plants. 

The  annexed  cut  represents  a  double  range  of  plant-pits, 
heated  by  wooden  tanks.  These  tanks  are  supplied  from  a 
small  boiler,  placed  in  the  centre,  between  the  two  pits ;  #,  end 
section,  shows  the  end  of  the  tank,  which  is  about  six  inches 
deep,  and  divided  into  two  compartments,  by  placing  a  slip  of 
wood  up  the  centre,  leaving  a  space  at  each  end,  for  the  water 
to  circulate  round.  The  arrows  show  the  course  of  the  water 
in  its  progress  round  the  tank ;  the  flow  and  return  pipes  are 
represented  by  dotted  lines.  These  tanks  are  merely  shallow 
boxes  of  wood,  occupying  nearly  the  whole  inner  area  of  the 
pits,  and  resting  on  piers  of  brick,  or  posts  of  wood  ;  rough 
pieces  of  wood  are  laid  crossways  over  the  tanks,  and  a  layer 
of  broken  bricks,  (or  sawdust,  if  the  pots  are  to  be  plunged, 
which  is  desirable,)  which  forms  the  bottom,  or  floor,  of  the  pit. 

It  is  truly  surprising  how  very  little  fire  is  required  to  main- 
tain a  perceptible  warmth  in  these  pits ;  and  the  growth  of  plants 
or  vegetables  of  any  description  is  astonishing.  In  some  nurs- 
eries these  pits  are  kept  continually  at  work.  The  lights  are 
entirely  thrown  off  them,  and  the  tops  thoroughly  exposed  to 
the  air ;  this  prevents  them  from  being  drawn  up  tender  and 
etiolated,  and  while  their  roots  are  stimulated  with  an  agreeable 
warmth,  they  have,  nevertheless,  all  the  strength  and  hardiness 
of  plants  grown  in  the  open  air. 

For  the  growth  of  early  melons  and  cucumbers  these  pits  are 
admirably  adapted ;  they  are  equally  efficient,  without  having 
the  disadvantages  of  dung-beds.  Their  neat  and  tidy  appearance 
gives  them  a  place  beside  the  other  hot-houses,  (which  is  not 
the  case  with  hot-beds  of  manure,)  to  none  of  which  they 
yield,  in  point  of  utility  or  interest. 

If  there  is  any  one  branch  of  exotic  horticulture  that  possesses 
more  extended  interest  than  another,  it  is,  undoubtedly,  the  cul- 


VARIOUS    METHODS    OF    HEATING   DESCRIBED    IN    DETAIL.        227 

Fig.  47. 


n 


u 


n 


20 


VARIOUS   METHODS    OF    HEATING   DESCRIBED   IN    DETAIL. 

ture  and  early  forcing  of  the  grape-vine.  The  increasing  im- 
portance of  this  branch  of  gardening  will  justify  me  in  devoting 
a  few  pages  to  that  subject.  The  culture  of  this  fruit  occupies 
a  very  high  position  in  this  country ;  volumes  and  pamphlets 
innumerable  have  been  written  about  it,  by  practicals,  theorists, 
and  experimentalists,  each  one  supposing  he  has  discovered 
something,  which,  for  want  of  more  extended  information,  he 
calls  "  new,"  in  the  managing,  heating,  or  ventilating  of  his 
vineries,  when,  lo !  another  starts  up  and  knocks  it  on  the  head, 
and  proposes  a  new  nostrum ;  and  every  one  is  sure  to  find 
some  ignorant  enough  to  follow  his  advice.  It  might  not  be  out 
of  place  here,  to  discuss  some  of  the  most  important  points  which 
an  extended  experience  has  proved  to  be  desirable,  in  the  heat- 
ing of  structures  for  the  culture  of  the  vine. 

And,  first,  let  me  remark,  that  nothing  is  more  creditable  than 
the  use  of  the  readiest  and  cheapest  means  at  hand  for  securing 
a  definite  result.  Whatever  system  may  be  thought  of,  it  is 
desirable  to  understand  the  principles  upon  which  it  rests  for 
its  success.  It  must  be  borne  in  mind,  in  the  outset,  that  no 
care  in  the  culture  of  the  vine,  under  glass,  will  compensate  for 
a  contaminated  atmosphere,  which  should,  at  all  times,  approach 
to  the  natural  summer  purity  and  warmth. 

Were  we  to  analyze  and  bring  into  view  the  first  principles 
of  horticulture,  and  make  ourselves  masters  of  the  various  effects 
produced  upon  the  grape-vine  under  glass,  and  the  causes,  we 
should  often  smile  at  the  ludicrous  importance  we  attach  to  par- 
ticular methods  of  practice.  A  blind  man,  by  habit,  will  often 
walk  along  a  devious  path,  with  quagmires  and  pitfalls  on  either 
side  of  him,  and  safely  too,  whether  at  midnight  or  noon-day ; 
and  we  often  follow  the  example  of  the  blind.  We,  in  one  way 
or  another,  acquire  the  faculty  of  performing  certain  operations 
with  a  life-like  certainty,  though  in  the  same  degree  of  mental 
darkness  as  regards  the  power  of  deviating  from  the  beaten 
track  without  committing  egregious  errors.  In  all  such  cases, 
there  can  be  no  doubt  that  it  is  wise  to  follow  the  old  trodden 
path,  till  we  can  more  plainly  see  which  is  the  safest  for  our 
particular  case.  It  does  not  so  much  signify  which  of  the  best 
methods  we  adopt,  provided  the  science  of  culture  has  given  us 


VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.     229 

sufficient  light  upon  the  nature  of  the  endless  variety  of  means 
and  methods  that  are  before  us,  which,  however  defective  they 
may  seem  in  the  hands  of  the  inexperienced,  may  be  safe  and 
certain  in  the  hands  of  the  skilful  practitioner. 

It  cannot  be  admitted,  however,  that  in  carrying  out  this 
principle  it  is  unnecessary  to  scrutinize,  with  the  utmost  exact- 
ness, the  facts  for  or  against  any  particular  system,  which  the 
fancy  of  gardeners  or  amateurs  may  choose  to  follow.  The  very 
fact  that  there  are  so  many  systems  of  warming  hot-houses, 
gives  increased  force  to  the  call  for  minute  record  of  experi- 
ments. Upon  no  safer  principle  can  our  knowledge  of  horticul- 
ture be  based,  so  that  those  who  are  its  patrons  and  votaries 
may  follow  principles,  founded  upon  facts,  and  not  upon  specula- 
tions. Hence  they  would  not  have  to  endure  the  inconvenience 
and  risk  of  being  dependants  upon  plausible  theories,  which 
practice  may  prove  to  be  absurd. 

A  great  deal  that  might  be  said  on  vineries,  in  regard  to  heat- 
ing them,  can  have  but  a  local  application ;  and,  in  some  places, 
no  application  at  all,  inasmuch  as  the  diversity  of  climate  in  the 
different  states  would  render  the  erection  of  an  apparatus  at  one 
place  necessary,  which  would  be  absolute  folly  in  another.  The 
erection  of  a  powerful  and  expensive  heating-apparatus  is  only 
required  where  the  forcing  of  the  vine  is  desired  in  winter,  under 
difficulties  of  intense  cold  and  long-continued  frost,  as  in  New 
England.  To  these  latter  circumstances  the  following  method 
will  chiefly  apply. 

Figure  48  shows  the  plan  of  a  winter  vinery,  i.  e.,  one  for 
forcing  in  winter;  a  is  the  border,  underneath  which  is  an 
arch  of  brick,  forming  a  chamber,  through  which  the  hot- 
water  pipes  are  made  to  travel,  after  going  round  the  house 
inside  for  atmospheric  heat.  The  cold  water  returns  again  into 
the  boiler  at  b. 

As  far  as  I  can  learn  —  and  I  have  made  many  inquiries  — 
this  system  of  applying  heat,  in  connection  with  vine-growing, 
has  not  yet  been  adopted  in  this  country ;  still,  it  may  be  in 
use,  since  the  obvious  utility  of  it  must  have  been  apparent  to 
those  who  are  engaged  in  the  culture  of  hot-house  grapes.  To 
recommend  such  an  expensive  system  as  this,  for  all  occasions 


230       VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 


Fig.  48. 


VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.     231 

and  under  every  circumstance,  would  be  folly.  But  its  utility 
in  winter-forcing,  especially  where  the  soil  is  damp  and  natu- 
rally cold,  will  be  obvious  to  any  one  of  much  experience  in 
these  matters.  The  greatest  success  has  attended  the  applica- 
tion of  border-heating,  in  England,  where  an  enormous  amount 
of  money  and  labor  is  annually  expended  upon  the  forcing  of 
grapes,  and  where  they  are  produced  in  great  perfection  all  the 
year  round. 

I  have  said  that  where  early  forcing  is  practised,  and  the  soil 
and  sub-soil  of  a  cold,  retentive  nature,  the  adoption  of  some 
method  similar  to  the  above  is  almost  indispensable  to  general 
success.  I  wish,  however,  to  be  rightly  understood,  and  not  to 
mislead,  and  therefore  advert  to  what  ever}7  gardener  knows  well, 
that  good  grapes  are  sometimes  produced  under  the  entire  neg- 
lect of  all  the  ordinary  precautionary  measures  resorted  to  by 
good  gardeners  for  the  purpose  of  securing  success. 

In  support  of  this  method  of  heating  borders,  I  will  briefly 
advert  to  the  opinions  of  some  of  the  leading  gardeners  in  Eng- 
land. Mr.  Fleming,  gardener  to  the  Duke  of  Sutherland,  at 
Trentham  Hall,  writes  to  the  Gardener's  Chronicle,  four  years 
ago,  to  the  following  effect :  —  "  Shrivelling  was  common  here, 
until  the  system  of  keeping  up  a  bottom  heat  in  the  vine  bor- 
ders was  introduced.  Since  then  there  has  been  no  appearance 
of  it,  except  in  a  late  house  last  year.  In  the  month  of  August 
we  had  a  great  deal  of  rain,  which  penetrated  the  border,  and 
the  weather  was  for  a  few  days  very  cold,  and  the  grapes,  which 
up  to  that  time  were  swelling  beautifully,  received  a  check,  and 
shortly  after  many  of  the  fruit-stalks  shrivelled." 

In  the  same  paper  Mr.  F.  makes  the  following  statement, 
which  is  the  strongest  evidence  of  the  utility  of  the  system  that 
has  come  under  our  notice :  —  "I  am  so  convinced,"  says  he, 
"  of  the  advantage  of  this  practice,  that  I  would  prefer  the 
introduction  of  flues  under  every  vine  border  about  the  place, 
did  circumstances  permit."  This  method  is  also  employed  at 
Welbeck,  with  the  greatest  success.  There  the  soil  and  sub- 
soil are  heavy,  cold,  and  wet ;  and  without  some  such  precau- 
tion, grape-growing  would  be  but  a  barren  business.  But  by 
this  method  of  chambering  the  borders,  and  other  good  manage- 
20* 


232    VARIOUS   METHODS    OF   HEATING   DESCRIBED   IN   DETAIL. 

ment  beside,  the  most  abundant  crops  are  obtained.  Mr.  Rob- 
erts, of  Raby  Castle,  author  of  a  treatise  on  vine  culture  under 
glass,  and  a  good  authority  on  the  subject,  says  :  —  "  Fault  has 
been  found  with  me  for  recommending  heat  to  the  roots  of  vines 
by  fermenting  manure,  on  account  of  its  unsightliness ;  but 
practice  convinces  me  that  without  a  corresponding  degree  of 
temperature  betwixt  the  root  and  top,  you  cannot  produce  good 
grapes.  I  intend,  however,  to  do  away  with  the  unsightliness 
of  manure,  in  my  new  vine  borders,  by  heating  them  on  another 
plan."  Such  is  the  testimony  of  men  who  stand  first  in  their 
profession,  —  men  of  undoubted  probity  and  extensive  expe- 
rience, and  who,  as  authorities  on  these  matters,  may  be  fully 
relied  on.  No  one,  who  once  has  seen  the  extensive  gardens 
which  they  superintend,  will  dispute  the  propriety  of  the  practice 
of  placing  fermenting  manure  on  the  surface  of  a  vine  border. 
But  I  must  differ  in  my  opinion  from  Mr.  Roberts  in  regard  to 
its  effects.  It  may  not  be  positively  injurious,  but  Mr.  Roberts 
has  failed  to  prove  that  it  is  positively  beneficial.  Moreover,  if 
he  has  succeeded  in  imparting  a  temperature  to  his  vine  border 
equal  to  the  atmosphere  at  which  he  keeps  his  vinery,  he  must 
have  a  'body  of  manure  equal  in  bulk  to  the  vinery  itself.  Heat 
travels  with  extreme  slowness  through  the  damp,  confined  air 
of  dung-beds,  and  the  difficulty  of  getting  heat  to  travel  down- 
wards is  well  known.  A  body  of  fermenting  material  may 
communicate  its  "heat  to  the  mere  surface  of  the  soil  on  which 
it  lies;  "but  the  moisture  it  absorbs  from  the  atmosphere,  as  well 
as  its  saturation  by  rains,  is  communicated  to  the  soil  in  place 
of  heat,  so  that  in  reality  the  good  produced  is  nearly,  if  not 
altogether,  counterbalanced  by  the  evil.  The  plan  Mr.  R. 
intended  to  adopt  has  not,  as  far  as  I  know,  been  made  public ; 
but  probably  it  was  some  kind  of  chambered  border,  with  arti- 
ficial heat  radiating  beneath  it. 

The  annexed  drawing  represents  a  chambered  border,  heated 
with  a  hot-water  tank,  which  is  supplied  with  water  from  the 
pipes  when  it  can  be  spared  from  the  atmosphere  of  the  house, 
by  a  tap  fixed  on  the  pipe,  as  shown  at  a,  in  the  end  section. 
If  the  water  is  allowed  to  flow  into  the  tank  from  the  boiler  for 
the  space  of  an  hour,  a  sufficiency  of  heat  will  be  communicated 


VARIOUS   METHODS    OF    HEATING    DESCKIBED   IN    DETAIL.       233 

.  J^       Fig.  .49. 


« 

.-!?-:  -.-asa-. 

234      VARIOUS   METHODS   OF   HEATING   DESCRIBED   IN    DETAIL. 

to  the  chamber,  and  the  border  for  maintaining  a  perceptible 
warmth  in  the  latter  for  twelve  or  fourteen  hours.  A  division 
is  made  in  the  tank  for  the  circulation  and  displacement  of  the 
water,  as  shown  by  the  arrows  in  Fig.  49.  Pigeon-hole  walls 
are  built  across  the  border,  about  five  feet  distant  from  each 
other.  Upon  these  rough  pieces  of  timber  are  laid,  as  a  bottom 
to  the  border ;  a  layer  of  brush-wood  (small  branches)  is  laid 
over  the  timber  to  prevent  the  soil  from  falling  through  upon  the 
tank.  The  rest  should  be  filled,  to  the  depth  of  two  feet,  with  a 
good  turfy  material,  with  a  plentiful  admixture  of  whole  bones 
and  rough  pieces  of  charcoal,  to  render  the  mass  as  porous  as 
possible,  for  the  admission  of  the  heat  upwards,  as  well  as  to 
maintain  an  equality  in  the  moisture  of  the  mass.  Shutters  are 
provided  for  covering  the  border,  which  may  lie  upon  the  same 
angle  as  the  roof,  or  otherwise,  as  the  front  wall  of  the  house 
corresponds  to  the  curb  in  front  of  the  border.  Ventilators  are 
placed  in  the  front  wall,  beneath  each  light,  for  the  admission 
of  air  into  the  house  ;  and  when  air  is  required  by  these  front 
ventilators,  the  shutters  covering  the  border  must  be  tilted  at 
the  lower  side,  when  the  air  passes  across  the  border,  through 
the  front,  into  the  house.  We  consider  this  mode  of  arrange- 
ment for  the  border  cheaper  and  better  than  that  of  arching  the 
chamber,  as  shown  in  Fig.  48,  although  both  are  equally  effect- 
ual, and  may  be  adopted  as  circumstances  may  suggest. 

If  chambered  borders  be  found  so  beneficial  in  England,  for 
winter  forcing,  where  the  frost  seldom  penetrates  more  than  a 
few  inches  into  the  ground,  and  rarely  continues  for  more  than 
a  few  days  at  a  time,  —  a  week  or  two,  at  the  longest,  —  surely 
it  must  prove  equally  if  not  more  serviceable  in  the  New  Eng- 
land states,  where  the  winters  are  so  intensely  cold  as  to  render 
the  forcing  of  grape-vines  at  that  time  next  to  impossible.  Still, 
if  the  forcing  of  this  fruit  can  be  carried  on  at  mid-winter,  at  a 
reasonable  cost,  there  is  no  reason  to  suppose  that  it  would  be 
unprofitable,  even  at  the  low  prices  at  which  grapes  are  usually 
sold  in  the  principal  markets  of  this  country.  All  cultivators 
are  aware  that  the  profits  of  fruit  culture  are  just  in  proportion 
to  the  economy  with  which  good  crops  can  be  produced  ;  and 
this  is  more  especially  the  case  in  the  culture  of  exotic  fruits, 


VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL.     235 

there  being  more  room  for  the  exercise  of  skill  in  their  produc- 
tion. 

Suppose,  for  instance,  that  we  take  the  calculations  of  Mr. 
Allen,  in  his  treatise  on  the  Culture  of  the  Grape-vine,  where, 
in  pp.  69,  70  and  71,  he  estimates  the  quantity  of  fermenting 
manure,  necessary  for  the  covering  and  warming  of  a  border 
100  feet  in  length  to  cost  $700;  which,  together  with  the 
other  items  of  management,  —  repairs,  fuel,  interest  on  cost, 
etc., —  to  amount  to  $1120.  The  produce  of  a  house  so 
heated  and  managed,  according  to  his  calculation,  is  on  an 
average  1067  pounds  of  fruit.  I  do  not  intend  to  dispute  the 
accuracy  of  these  calculations,  although  they  appear  startling 
enough.  And  doubtless  Mr.  Allen  has  had  data  sufficiently 
accurate  and  authoritative,  from  which  to  draw  his  deductions ; 
and  hence  I  consider  myself  justified  in  making  them  partially 
the  data  of  mine. 

And,  admitting  the  beneficial  effect  of  fermenting  manure  to 
be  all  that  its  advocates  claim  for  it,  let  us  compare  the  calcula- 
tions above,  with  the  cost  and  working  of  chambered  borders  ; 
and,  by  balancing  the  two  together,  we  shall  be  the  better  able 
to  estimate  the  merits  of  each  on  the  score  of  economy. 

In  order  to  effect  this,  I  have  been  at  some  pains  to  obtain  the 
probable  expense  of  such  a  border  as  that  represented  on  page 
232,  Fig.  49  ;  and,  in  making  my  calculations,  I  have  placed  my 
figures  rather  above  than  under  the  estimate ;  so  that,  should 
I  make  any  error,  it  will  be  on  the  most  favorable  side. 

To  make  a  chambered  border  100  feet  long,  we  have  — 

For  brick  work, $200 

Timber  to  form  the  bottom  of  the  border,  ....    60 

Tank, 50 

Extra  piping  for  do., 10 

Extra  fuel, 15 

Excavating  the  border, 45 

Shutters,  &c.,  for  covering  do., 100 

$480 

Now,  if  we  subtract  480  from  700,  (the  cost  of  manure,)  we 
have  a  saving  of  $220,  the  very  first  season ;  or,  in  other 


236    VARIOUS    METHODS    OF    HEATING   DESCRIBED    IN    DETAIL. 

words,  the  manure  required  for  one  year  costs  more  than  the 
making  of  this  border,  by  $220.  Then,  if  we  estimate  the  an- 
nual expenditure  on  account  of  the  border,  for  heating,  repairs, 
etc.,  to  be  $25,  we  have  $700,  the  cost  of  manure,  minus 
$25,  the  cost  of  the  tank  border,  which  gives  an  annual  saving 
of  no  less  than  $675  by  this  method  of  heating. 

It  may  be  supposed  that  a  body  thus  situated  over  a  hot- 
water  tank,  might  be  too  rapidly  dried  by  the  ascending  heat. 
But  this  is  only  a  supposition ;  and  in  practice  it  amounts  to 
nothing  more,  for  the  warmth  generated  by  the  tank  is  so  grad- 
ual, and  spread  over  so  large  a  surface,  that  the  heat  is  equally 
distributed,  and  no  part  of  the  mass  is  overheated,  or  one  part 
heated  above  another.  And,  indeed,  one  would  scarcely  believe, 
from  the  small  quantity  of  heat  thus  generated,  that  so  striking 
an  effect  would  be  produced ;  of  course,  the  border  must  not  be 
allowed  to  get  too  dry.  Nor  will  this  be  a  matter  of  so  much 
difficulty  as  may  appear,  as  two  or  three  good  soakings  with 
water,  —  or,  what  is  better,  weak  liquid  manure,  —  will  generally 
suffice,  until  the  weather  permits  you  to  uncover  the  border 
during  the  middle  of  a  wet  day,  covering  it  up  again  before 
evening.  The  operation  of  watering  will  be  much  facilitated 
by  having  a  hose  fitted  to  the  tap  of  a  cistern  containing  rain- 
water inside  the  house  ;  and  no  hot-house  of  any  kind  should  be 
without  such  an  appendage.  If  the  mechanical  texture  of  the 
soil  be  good,  the  water  soon  finds  its  way  through.  The  larger 
portion  of  the  moisture  being  held  in  suspension  by  the  lower 
stratum  of  soil,  becomes  gradually  warmed  by  the  tank,  and  is 
again  carried  upwards  by  the  heated  air ;  so  that  the  roots  of 
the  vines  have  the  full  advantage,  not  only  of  the  heat,  but  of 
the  moisture.  The  abstraction  of  heat  may  be  in  a  great  meas- 
ure prevented,  in  excessively  frosty  weather,  by  laying  a  few 
inches  thick  of  straw,  or  stable  litter,  immediately  over  the  soil 
beneath  the  covering.  This  is  merely  a  precautionary  expedient, 
and,  though  useful,  will  seldom  be  necessary. 

In  the  formation  of  a  chambered  border  many  alterations  and 
improvements  will  suggest  themselves  to  the  mind  of  the  practi- 
cal man,  which  could  not  be  very  conveniently  represented  in 
the  accompanying  sketches.  For  instance,  as  a  covering, 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.          237 

instead  of  shutters,  I  would  decidedly  prefer  glass  ;  and  where 
there  are  plenty  of  spare  sashes  about  the  place,  they  might  be 
used  in  this  way,  with  much  advantage,  just  as  spare  sashes  are 
used  for  covering  peach  and  apricot  wall-trees  in  England.  But 
suppose  that  sashes  of  sufficient  length  were  provided  for  the 
purpose ;  the  expense  would  probably  be  counterbalanced  by  the 
advantage  gained.  For  a  house  100  feet  long,  25  sashes  would 
be  required,  which,  at  3  dollars  each,  would  be  75  dollars;  a 
very  trifling  sum  when  a  desirable  object  is  to  be  attained  by  the 
judicious  expenditure  of  it.  And,  in  this  case,  although  it  may 
appear  injudicious  to  some,  the  object  is,  in  my  opinion,  suf- 
ficiently important  to  justify  this  expense.  Light  absorbed  is 
productive  of  heat,  especially  if  the  absorbing  body  be  of  a  dark 
color,  for  then  it  is  absorbed  without  being  again  reflected  upon 
the  transparent  medium.  Hence  we  see  the  advantage  of  hav- 
ing the  border  covered  with  a  body  admitting  light;  and  the  soil 
of  which  the  surface  of  the  border  is  composed,  of  a  dark  color, 
that  the  heat  which  falls  upon  it  may  be  absorbed  and  retained. 

For  winter  forcing,  small  houses  are  decidedly  preferable  to 
large  ones.  Houses  about  25  or  30  feet  long  are  sufficiently 
large,  and  are  more  easily  heated,  and  more  convenient  to  man- 
age. Even  in  the  milder  climate  of  England,  small  vineries 
are  preferred  to  large  ones,  and  are  found  to  be  more  profitably 
worked.  Above  all  things,  loftiness  should  be  guarded  against, 
as  being  the  very  worst  feature  in  a  forcing-house,  as  the  heated 
air  continues  to  ascend  upwards;  and,  unless  the  external 
atmosphere  can  be  admitted  at  the  top,  the  vines  at  that  portion 
of  the  house  will  always  be  in  a  state  of  vegetable  suffocation; 
a  fact  of  too  frequent  occurrence,  in  lofty  houses,  even  in  sum- 
mer, and  which  is  rendered  still  more  injurious  by  the  present 
defective  methods  of  ventilation. 

A  few  words  more  regarding  the  permanency  of  these  borders. 
Assuming  that  a  proper  command  of  heat,  both  for  the  atmos- 
phere and  the  soil,  is  obtained,  the  question  has  been  asked,  How 
long  will  borders,  so  circumscribed,  continue  to  supply  a  house  of 
grape-vines  with  the  requisite  nourishment  ?  This  question  has 
hitherto  proved  a  drawback  to  the  adoption  of  these  borders  by 
many  who  have,  in  every  other  respect,  the  highest  opinion  of 


238        VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL. 

the  advantages  to  be  derived  from  them.  In  short,  they  are 
afraid  the  vines  will  exhaust  the  soil  within  the  limits  of  the 
range  allowed  to  the  roots,  and  then  fail  in  producing  a  crop  for 
the  want  of  food.  Now  I  think  a  very  little  consideration  will 
prove  this  to  be  a  groundless  fear.  Supposing  the  soil  to  be  the 
principal  repository  for  the  nutriment  of  the  vines,  and  that  it 
should  contain  all  the  substances  in  abundance,  whether  solid 
or  gaseous,  which  form  their  structure  and  produce  their  fruit ; 
yet  it  is  not  necessary  to  form  this  border  into  a  mass  of  nitro- 
geneous  matter  to  produce  these  results.  Plants,  in  this  respect, 
are  as  bad  as  animals ;  and  a  vine-border  may  as  readily  be 
poisoned  with  excess,  as  impoverished  for  the  want  of  proper 
elements  of  nutrition.  Now  I  maintain,  and  I  do  so  upon  expe- 
rience, that  the  grand  requisite  to  be  looked  to  in  the  formation 
of  a  vine-border  is  its  condition  as  regards  texture,  and  not  its 
chemical  properties.  The  first  secured,  the  latter  can  be  added, 
not  only  when  it  is  first  made  up,  but  annually  afterwards,  and 
each  subsequent  time,  with  as  much  advantage  as  at  the  begin- 
ning. "  The  food  of  vines  consists  chiefly  of  the  elements,  car- 
bon, hydrogen,  nitrogen,  and  oxygen,  in  some  state  of  combina- 
tion, together  with  certain  inorganic  compounds,  amounting  to 
only  about  7  per  cent.,  as  silica,  salts  of  lime,  magnesia,  iron, 
potash,  soda,  and  other  bases,  combined  with  sulphuric,  phos- 
phoric, carbonic,  silicic,  humic,  and  other  acids.  These  sub- 
stances can  be  supplied,  in  a  liquid  state,  in  quantities  more  than 
sufficient  for  the  actual  requirements  of  the  vine.  But  their 
efficacy  will  very  much  depend  upon  the  freeness,  porosity,  and 
other  mechanical  qualities  of  the  soil,  favorable  to  the  decom- 
position and  recombination  of  these  elements.  The  general 
method  of  renovating  a  vine-border  is  by  incorporating  about 
half  its  bulk  of  manure,  to  the  manifest  destruction  of  many  of 
the  best  roots,  —  for  the  best  are  always  on  the  surface, — 
besides  incurring  a  vast  amount  of  labor  and  expense,  which 
labor  and  expense  would  be  sufficient  for  at  least  a  dozen  years. 
Salts  of  ammonia,  for  instance,  in  their  various  states  of  com- 
bination, are  known  to  exercise  a  powerful  influence  on  the 
growth  of  grape-vines.  Now,  by  adding,  say,  10  tons  of  the 
best  manure  to  the  borders,  we  supply  them  with  about  85  pounds 


VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL.         239 

of  ammonia,  in  the  form  of  sulphate,  carbonate,  nitrate,  and 
muriate  of  ammonia.     Now,  the  same  quantity  will  be  fur-  • 
nished  by  one  quarter  of  a  ton  of  good  Peruvian  guano,  at  prob- 
ably one  half  the  cost,  while  its  application,  in  a  liquid  state,  is, 
more  immediately  beneficial  to  the  vines.     The  same  salts  are 
supplied  from  urine,  which  ought  to  be  collected  in  tanks  for 
that  purpose.     By  the  addition  of  these  elements,  an  impover- 
ished border,  incapable  of  yielding  one  fifth  of  a  crop,  has  been 
enriched  and  made  to  produce  good  crops  of  fruit.     As  I  have 
said,  however,  I  would  have  a  border  made,  say,  12  or  16  feet 
wide,  of  good  open  material,  not  over-rich  in  nitrogeneous  mat- 
ter, but  abundantly  mixed  with  lumps  of  charcoal,  and  plenty  of 
bones ;  a  quantity  of  common  lime-stone  (carbonate  of  lime) 
might  be  laid  on  the  bottom,  and  mixed  through  the  mass. 
With  a  border  so  formed,  about  2  feet  deep,  and  14  feet  wide, 
by  the  regular  application  of  nutritious  elements  in  a  liquid 
form,  and  proper  management  in  other  respects,  the  most  abun- 
dant crops  may  be  produced,  for  at  least  a  quarter  of  a  century. 
We  are  well  aware  of  the  arguments  that  are  brought  to  bear 
against  shallow  vine-borders  in  this  country,  from  their  greater 
liability  to  become  dried  up  by  the  parching  droughts  of  sum- 
mer.    But  here  this  argument  can  have  no  application,  as  the 
season  of  forcing  is  at  that  period  when  the  ground  is  saturated 
with  wet,  and  little  or  no  abstraction  of  it  by  the  atmosphere. 
And  as  the  temperature  of  any  piece  of  ground  is  nearly  in 
exact  proportion  to  the  amount  of  water  it  contains,  so  it  follows 
that  a   vine-border  saturated  with  water   must  necessarily  be 
colder,  and  consequently  more  injurious  to  forcing  plants,  than 
a  dry  one,  even  without  heat!     It  is  true,  a  border  may  be 
drained,  and  all  superfluous  and  stagnant  moisture  carried  off, 
but  even  the  driest  and  most  silicious   soils   have  a  certain 
capacity  of  suspending  moisture,  in   their  pores,  and  as   this 
capacity  is  greater  in  soils  containing  much  organic  matter  than 
in  those  of  a  more  sandy  nature,  it  follows  theoretically,  —  and 
we  find  it  so  in  practice,  —  that  rich  borders  are  colder  and 
wetter  than  the  common  garden  soil.     I  believe  this  is  a  fact 
which  no  one  will  dispute.     But  however  warm  vine-borders 
may  be  by  their  natural  position,  or  rendered  so  by  artificial 
21 


240        VARIOUS  METHODS  OF  HEATING  DESCRIBED  IN  DETAIL. 

drainage,  they  must  still  be  very  far  from  the  internal  tempera- 
ture of  the  house,  —  a  fact  which  requires  no  calculation  to 
prove  it.  And  hence,  although  the  vine,  of  all  other  fruit-bear- 
ing plants,  will  accommodate  itself  to  circumstances  apparently 
the  most  unpropitious,  and  will  stand  forcing  in  mid-winter  bet- 
ter than  any  other  fruit  we  can  place  into  a  hot-house,  still,  it 
cannot  be  expected  that  we  shall  arrive  at  anything  like  perfec- 
tion in  its  produce  by  winter-forcing,  under  the  present  methods 
of  cultivation.  And  we  know  that,  whatever  can  be  said  in 
favor  of  carrion-borders,  no  mere  aggregation  of  organic  matter 
will  suffice  for  the  production  of  grapes,  especially  in  winter, 
if  the  principle  of  life  be  impotent,  and  the  functions  of  the  plant 
impaired,  whether  by  natural  or  artificial  causes  ;  and  nothing 
is  more  likely  to  weaken  the  one,  or  impair  the  other,  than 
placing  the  roots  of  vines  in  an  ice-house,  and  the  branches  in 
an  oven. 

In  close  connection  with  the  foregoing  subject  is  a  system 
which  has  engaged  no  inconsiderable  share  of  attention  in  Eng- 
land, and  may  probably  be  employed  with  equal  advantage  in 
this  country.  The  system  to  which  I  allude,  is  forcing  by  hot 
walls  covered  with  glass.  It  has  now  become  common  to  build 
garden  walls  hollow,  and  heat  them  with  hot  water,  with  flues, 
or  both,  and  by  covering  them  with  temporary  roofs,  consisting 
either  of  spare  sashes  on  hand,  or  by  having  sashes  made  for 
the  purpose.  By  this  means,  a  range  of  portable  houses  may 
be  constructed  upon  any  walls  adapted  for  that  purpose,  at  a 
very  inconsiderable  expense,  compared  with  that  of  permanent 
houses.  —  (See  Part  I.  Construction  of  Walls.) 

Fig.  50  shows  an  end  section  of  the  wall ;  a  a,  ties  across  the 
wall,  at  regular  distances,  for  the  purpose  of  strengthening  the 
fabric ;  b,  the  pipes  for  hot  water,  or  the  situation  of  the  flue,  if 
that  method  of  heating  be  adopted ;  c,  the  furnace  and  boiler, 
placed  in  a  recess  of  the  wall,'  as  shown  in  the  ground  plan ;  d 
d,  the  returning  pipes,  or  the  position  of  the  returning  flue,  if 
pipes  are  not  used ;  e,  the  projecting  support  for  the  sashes 
under  the  coping;  /,  the  lower  supports  for  the  sashes,  consist- 
ing of  timber  posts  driven  into  the  ground,  that  no  obstruction 
may  be  presented  to  the  roots  of  the  vines  by  a  brick  wall ;  g, 


VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.       241 
Fig.   50. 


I 


242     VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN   DETAIL. 

the  sashes ;  h  h  k,  are  square  tubes  of  wood,  penetrating  the 
soil  to  the  chamber  beneath,  to  let  the  heat  rise  up  into  the 
space  confined  within  the  sashes  and  the  wall ;  the  number  of 
these  opening's  depending  entirely  upon  the  weather,  and  the 
season  of  forcing.  They  may  be  closed  with  a  lid  when  the 
sashes  are  removed.  From  the  foregoing  description,  it  will  be 
perceived  that  an  erection  of  this  kind  has  all  the  advantages 
of  a  house,  —  at  least  as  far  as  grape-growing  is  concerned, — 
without  the  consequent  expense,  and  when  once  all  the  mate- 
rials are  properly  adjusted,  they  can  be  removed,  or  replaced,  by 
almost  any  gardener,  without  the  aid  of  a  tradesman.  The 
rafters  are  merely  fastened  to  a  plate  of  wood,  about  one  foot 
broad,  and  two  inches  thick,  by  means  of  iron  pegs,  as  at  e, 
in  the  end  section,  and  also  at  the  bottom  to  another  plate,  sim- 
ilar to  the  one  above,  and  fitted  into  the  posts  at  f;  the  sashes 
are  fixed  to  the  rafters  by  means  of  a  latch,  or  thumb-screw, 
placed  within  reach  of  the  operator,  for  the  facility  of  admitting 
air.  This  is  effected  by  letting  down  the  sashes  to  any  distance, 
and  supporting  them  by  notched  brackets,  or  letting  them  down 
to  the  ground,  if  necessary,  as  shown  by  the  dotted  line,  at  /. 

This  method  may  be  adopted  without  having  any  cavity 
beneath  the  border,  and,  of  course,  will  be  cheaper,  although  we 
would  decidedly  prefer  such  a  cavity,  did  circumstances  permit. 
The  advantage  of  hollow  walls,  warmed  by  some  method,  has 
been  long  well  known  to  gardeners,  and  so  highly  are  they 
thought  of  in  England,  that  scarcely  any  garden  of  consequence 
is  without  them.  Indeed,  in  the  majority  of  seasons,  the  culture 
of  the  vine,  peach,  nectarine,  apricot,  and  fig,  —  even  on  walls, — 
would  be  a  very  precarious  and  uncertain  business,  although 
the  method  of  covering  such  walls  with  portable  glass  has  but 
very  lately  been  brought  into  use,  and,  now  that  glass  is  cheaper 
in  that  country,  is  almost  certain  to  be  extensively  applied  to 
this  purpose.  In  one  or  two  cases  we  have  seen  this  method 
adopted  with  astonishing  success,  and  without  any  cavity,  or 
any  other  preparation  than  the  common  border  and  wall  of  the 
garden.  In  one  place  we  had  forty  feet  of  a  wall  thus  covered 
with  spare  sashes ;  the  space  included  some  peach  and  fig 
trees,  in  excellent  bearing  condition,  and  well  set  with  buds, 


VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL.      243 

giving  promise  of  a  fair  crop.  The  wall  was  covered  with  the 
glass  on  the  first  of  February,  but  no  heat  was  applied  to  the 
wall  until  the  beginning  of  March.  The  sashes  were  fixed 
exactly  as  we  have  described  in  the  foregoing  sketch.  The  wall 
and  fire-place  were  precisely  the  same,  but  no  cavity  was  be- 
neath the  border.  The  result  was,  that  the  crop  ripened  five 
weeks  earlier  than  those  on  the  same  wall,  uncovered,  without 
heat,  and  nearly  four  weeks  earlier  than  those  on  the  same  wall, 
with  heat,  and  covered,  in  the  usual  way,  with  netting.  Now 
this  was  merely  an  experimental  result,  without  much  previous 
preparation,  save  the  covering  up  of  the  wall  a  month  earlier 
than  the  warming  commenced,  —  if,  indeed,  this  can  be  called  a 
preparation,  —  being  an  absolutely  necessary  prerequisite  to  suc- 
cess, under  any  method  of  forcing.  When  the  warm  weather 
set  in,  the  sashes  and  rafters  were  taken  away,  and  the  enclosed 
part  received,  during  the  season,  the  same  treatment  as  the 
other  portions  of  the  wall. 

In  forming  a  hollow  wall,  there  will  be  quite  as  much  saved 
by  the  internal  cavity  as  will  suffice  to  warm  it,  as  only  about 
one  half  the  quantity  of  bricks  are  required ;  and  even  without 
a  heating  apparatus,  hollow  walls  are  superior  to  solid  ones,  for 
horticultural  purposes  ;  for,  under  all  circumstances,  they  are 
found  to  be  both  warmer  and  drier.  The  addition  of  a  heating 
apparatus,  however,  will  render  the  wall  a  very  useful  auxiliary 
to  the  forcing-house,  and  the  cost  will  be  amply  compensated  by 
the  utility.  By  looking  at  the  foregoing  plan,  it  will  be  seen 
that  the  furnace  is  placed  in  the  foundation  of  the  wall,  with  a 
few  steps  to  descend  to  it,  the  whole  being  covered  with  a  trap- 
door, leaving  nothing  unsightly  open  to  the  view  of  the  visitor. 

In  many  parts  of  this  country,  grapes  are  frequently  overtaken 
by  the  autumn  frosts,  before  they  are  ripened,  and  in  many 
others,  they  do  not  ripen  at  all.  Now,  it  is  obvious,  that  it  is 
neither  owing  to  a  deficiency  of  sun-light,  nor  a  deficiency  of 
heat,  for  in  Britain  the  quantity  of  both  are  much  less,  and  the 
quality  of  the  latter  less  powerful  for  the  maturation  of  fibre  and 
fruit ;  and  yet  it  is  common  enough  to  have  good  crops  of  (what 
in  America  are  called  foreign)  grapes,  on  the  open  walls.  In 
ordinary  seasons,  the  black  Hamburg,  Muscadine,  and  Fron- 
21* 


244      VARIOUS    METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 

tignacs,  ripen  well  in  the  open  air,  on  southern  aspects ;  and  in 
all  seasons  they  succeed  in  ripening  their  fruit,  in  tolerable  per- 
fection, on  hollow  walls,  with  a  little  heat  in  spring,  if  the 
season  be  backward,  and  a  little  in  autumn,  if  the  season 
be  late,  i.  e.,  if  cold  weather  should  set  in  unusually  early, 
which  it  frequently  does  in  Scotland ;  and  yet  we  have  seen  tol- 
erable crops  of  grapes  produced  north  of  the  Tweed,  on  heated 
walls,  without  any  glass  at  all.  This  statement  may  be  received 
with  incredulity  by  some,  who  have  had  poor  success  in  the 
cultivation  of  foreign  grapes,  in  the  open  air,  in  this  country, 
under  circumstances  of  climate  unquestionably  more  favorable 
than  can  be  found  in  any  part  of  the  British  Islands.  We  believe 
this  statement  will  be  corroborated  by  the  testimony  of  every 
one  who  is  acquainted  with  the  nature  of  the  climate  of  both 
countries.  In  fact,  so  much  are  people  in  this  country  impressed 
with  the  unfavorable  nature  of  an  English  summer,  that  in  all 
journals,  magazines,  periodicals,  and  papers,  of  every  descrip- 
tion, we,  without  one  single  exception,  find  it  qualified  with  the 
words,  dull,  gloomy,  austere,  wet,  cold,  damp,  dripping,  and 
many  other  appellations  of  similar  import,  which  it  is  not  my 
present  purpose  either  to  confirm  or  confute.  But  as  there  has 
not,  as  yet,  been  ,(as  far  as  we  can  learn)  any  general  cause 
assigned  for  the  general  failure  here,  there  is  but  one  infer- 
ence that  can  fee  drawn  from  the  above  statements,  viz.,  that 
there  must  be,  in  this  country,  something  wrong,  or  something 
wanting,  in  the  modes  of  cultivating  foreign  grapes,  in  the  open 
air.  It  cannot  be  said  that  the  summers  are  too  hot  for  the 
grape-vine ;  for  there  is  hardly  another  plant  in  the  vegetable 
kingdom,  that  will  bear  a  greater  amount  of  natural  or  artificial 
heat,  or  greater  alternations  of  heat  and  cold,  under  circum- 
stances otherwise  favorable.  There  is  no  degree  of  heat,  to 
which  natural  vegetation  is  subjected  in  this  country,  under 
which  it  will  not  nourish,  provided  the  intense  rays  of  the  noon- 
day sun  be  not  concentrated  upon  its  foliage ;  and  it  is  a  well- 
known  fact,  that  grape-vines  will  not  produce  fruit  abundantly 
when  they  are  not  in  a  favorable  aspect.  There  can  be  little 
doubt  that  we  must  look  to  the  condition  of  the  plant,  during 
the  spring  and  autumn,  to  enable  us  to  reach  the  cause,  and 


VARIOUS   METHODS    OF    HEATING    DESCRIBED   IN    DETAIL. 


245 


this  appears  to  be  substantially  proved,  by  the  invariable  success 
that  has  attended  the  culture  of  foreign  grapes  in  cold  houses,  as 
well  as  other  facts  suggested  by  experience,  in  the  culture  of 
that  noble  fruit.  The  value  and  importance  of  the  grape-vine 
have  already  induced  me  to  dwell  longer  on  this  subject,  in  con- 
nection with  heating,  than  I  intended  ;  I  therefore  consider  it 
foreign  to  my  subject  to  enlarge  further  on  its  culture,  although 
there  is  great  room  for  speculation,  theory,  experiment,  and 
practical  improvement.  Indeed,  it  would  be  difficult  for  the 
practical  horticulturist  to  take  hold  of  a  subject  affording  a  wider 
field  for  successful  experiment,  and  holding  out  brighter  hopes 
of  beneficial  results. 

Before  concluding  this  chapter  on  heating,  I  will  briefly  notice 
another  system,  more,  however,  on  account  of  its  novelty,  than 
applicability  to  the  warming  of  hot-houses,  although  it  has,  in 
some  instances,  been  applied  to  this  purpose.  I  refer  to  the 
method  of  heating,  by  which  the  hot  air  is  carried  along  by  the 
power  of  a  steam-engine.  This  system  is  applied  to  the  warm- 
ing of  large  factories  in  England,  and  has  been  also  applied,  with 
apparent  success,  in  some  large  nursery  gardens,  in  Germany. 
The  following  description  is  from  the  pen  of  Mr.  Marnock,  the 
able  editor  of  the  "  Gardener's  Journal,"  (Eng.,)  and  drawn  from 
his  own  observations  of  the  apparatus,  while  visiting  the  gardens 
of  Baron  Hugel,  near  Schonbrunn,  where  the  system  was  in 
operation  at  the  time. 

"  The  most  remarkable  feature  about  this  garden  is  the  mode 
of  heating,  which  we  shall  now  attempt  to  describe.  In  the 
first  place,  there  is  a  large  fire-place  constructed  ;  through  this 
fire-place  two  or  more  pipes  are  introduced ;  the  pipes  are  of  cast- 
iron  ;  one  end  of  these  pipes  communicates  with  the  common 
atmosphere,  the  opposite  end  being  introduced  into  a  large  box, 
or  flue ;  in  this  flue  is  placed  a  fan,  driven  by  a  steam-engine, 
which  fan  is  made  to  revolve  in  this  air-flue,  at  a  short  distance 
from  the  fire-place.  It  will  readily  be  understood,  that,  when 
the  fire  is  in  action,  with  those  iron  pipes  passing  through  it, 
and  terminating  in  the  large  air-flue,  the  revolving  action  of 
the  fan,  in  a  direction  to  draw  the  common  atmospheric  air 
through  the  iron  pipes  in  the  fire-place,  will  also  force  the  heated 


246       VARIOUS    METHODS    OF    HEATING    DESCRIBED    IN    DETAIL. 

air  onwards  to  the  other  end  of  the  flue,  and  thence  through  tin, 
zinc,  or  any  other  kind  of  pipe  placed  there  to  convey  it  away. 
By  these  means  it  is  conducted  (i.  e.,  the  heated  air  from  the 
box)  into  the  different  stoves  and  green-houses.  Each  house, 
or,  rather,  each  compartment,  is  provided  with  a  supply-pipe  and 
a  tap,  by  which  heated  air  is  admitted  by  measure,  and  of  course 
regulated  according  to  the  requirements  of  the  plants.  We 
could  not  clearly  ascertain  the  exact  size  of  the  fire-place,  but 
we  saw  some  iron  pipes,  which  we  were  told  were  similar  to 
those  in  use  in  the  fire-place  for  heating  the  air,  and  we  sup- 
posed them  to  be  about  six  inches  in  diameter.  These  pipes, 
as  they  are  exposed  to  the  action  of  a  strong  fire,  become  greatly 
heated,  and  the  air,  in  passing  through  them,  becomes  intensely 
hot  and  dry,  consequently,  deprived  of  its  oxygen  and  aqueous 
properties.  Here,  however,  no  evaporating  pans  are  used  for 
moistening  the  warm  air,  as  in  common  hot-air  furnaces,  and 
the  method  adopted  for  supplying  the  heated  air  with  moisture 
is  quite  as  novel  as  the  system  itself.  To  effect  this,  a  steam 
jet  is  played  into  the  hot-air  flue,  immediately  before  it  enters  the 
different  compartments,  and  Mr.  Hooibrink,  the  gardener  to 
Baron  Hugel,  stated  that  he  admitted  the  steam  according  to 
the  nature  of  the  plants  cultivated  in  each  apartment.  Thus, 
he  allowed  so  many  feet  of  steam  for  his  orchards ;  so  many  for 
his  stove  plants,  and  so  many  for  his  common  green-house 
plants ;  thus  each  kind  of  plants  is  supplied  with  steam, 
according  as  it  requires  a  moist  or  dry  atmosphere. 

"  Thus,  if  we  are  rightly  understood,  there  is,  first,  a  large  fire- 
place ;  through  this  fire  two  or  more  cast-iron  pipes,  six  inches 
in  diameter,  are  passed ;  they  are  so  placed  as  to  be  subjected  to 
the  most  intense  action  of  the  caloric  produced  by  combustion ; 
one  end  of  these  pipes  is  exposed  to  the  external  atmosphere, 
the  other  ends  enter  a  large  oblong  box,  on  a  level  with  the 
pipes,  in  which  is  placed  a  fan,  similar  to  those  used  in  small 
fanning  mills.  This  fan  is  made  to  revolve  with  considerable 
rapidity,  by  the  power  of  a  small  steam-engine,  drawing  the 
atmospheric  air  inwards  through  the  tubes  exposed  to  the  fire, 
and  forcing  it  onwards  through  the  main  conductor,  and  thence 
into  the  smaller  tubes  leading  to  the  right  or  left,  up  or  down, 


VARIOUS   METHODS    OF    HEATING    DESCRIBED    IN    DETAIL.       247 

as  the  case  may  be,  for  the  supply  of  the  mansion,  and  the 
several  hot-houses,  all  of  which  are  heated  by  the  same  appara- 
tus. Here  the  air  is  moved  and  replaced,  not  only  by  its  own 
density,  as  in  the  common  methods  of  hot-air  heating,  but  it  is 
drawn  rapidly  inwards  by  the  suction  of  the  fan  on  the  one  side, 
and  driven  onward  by  its  propulsive  power  on  the  other ;  and 
thus  it  appears  the  heat  travels  with  great  rapidity,  and  within 
a  few  minutes  after  the  heated  air  is  turned  on  the  apartment, 
and  moistened  as  may  be  desired  by  the  jet  of  steam  already 
described."*1 

*  Fans  are  now  frequently  employed  for  effecting  ventilation,  and 
are  generally  connected  with  the  heating  apparatus.  They  have  never, 
as  far  as  we  know,  been  employed  for  this  purpose  in  any  kind  of  hor- 
ticultural structures,  although  we  can  see  no  reason  why  they  should 
not  be  so.  This  will  be  again  referred  to,  when  we  come  to  treat  on 
that  part  of  our  subject. 


PART   III.     VENTILATION. 

SECTION    I. 

PRINCIPLES      OF     VENTILATION. 

1.  THE  ventilation  of  hot-houses,  either  in  summer  or  win- 
ter, constitutes  an  important,  if  not  the  most  important,  item  of 
their  general  management,  as  it  bears  more  directly  upon  the 
condition  of  the  external  and  the  internal  atmosphere.  It  re- 
quires, therefore,  the  strictest  attention  of  the  gardener  at  all 
seasons  of  the  year.  For,  important  as  other  things  connected 
with  exotic  horticulture  may  be,  —  light,  for  instance,  —  it  is, 
nevertheless,  more  under  the  gardener's  control,  and  more  sub- 
ject to  his  will.  He  places  his  plants  within  a  transparent 
medium,  which  is,  in  its  general  surface,  impermeable  to  the 
atmospheric  air;  and  he  forms  for  them  an  artificial  atmos- 
phere, which  is  invigorating,  or  the  reverse,  according  to  his 
knowledge  of  the  laws  that  regulate  the  atmosphere,  or  the 
general  principles  of  aerometry.  Notwithstanding  the  many 
discoveries  that  have  been  made  regarding  the  properties  of  air, 
I  have  been  unable  to  find  any  work  bringing  these  discoveries 
to  bear  upon  the  airing  of  hot-houses.  It  is  true  this  must  be 
accomplished  by  the  "  practical "  man,  and  the  sooner  we  begin 
to  think  about  it  the  better.  Every  horticulturalist,  no  matter 
what  his  department  in  the  vineyard  may  be,  soon  discovers  the 
necessity  of  maintaining  a  continual  warfare  with  its  different 
conditions  of  purity  and  impurity,  its  aridity,  and  its  moisture. 
We  have,  indeed,  various  theories  propounded  by  physiologists, 
regarding  the  power  of  plants  to  withstand  these  vicissitudes, 
some  of  which  have  their  general  principles  as  yet  enveloped  in 
a  mist  of  shadowy  vagueness. 

Many  remarkable  facts,  however,  might  be  mentioned  relative 


PRINCIPLES    OF    VENTILATION. 

to  the  qualities  and  quantities  of  certain  atmospheric  elements 
which  plants  are  capable  of  sustaining  in  deficiency  or  in  excess. 
And  the  one  or  the  other  of  these  conditions  appears  to  some  of 
the  species  a  natural  and  even  a  necessary  circumstance.  The 
degree  in  which  vitality  is  sometimes  retained  by  plants,  under 
the  most  unfavorable  conditions,  for  a  period  to  which  it  is  diffi- 
cult to  assign  a  limit,  is  one  of  the  most  interesting  and  curious 
circumstances  in  their  economy.  Instances  have  been  related 
of  the  growth  of  bulbs,  unrolled  from  among  the  bandages  of 
Egyptian  mummies.  Although  there  is  good  reason  to  believe 
that  deception  has  been  practised  on  this  point,  upon  the  credu- 
lity of  travellers,  still  there  is  nothing  impossible  in  the  asserted 
fact.  Light,  heat,  and  moisture  are  the  cause  of  the  development 
of  these  curious  structures,  and  their  forms  become  expanded 
under  the  additional  agency  of  atmospheric  air.  Now,  when 
removed  from  the  influence  of  these,  there  is  no  reason  why  a 
bulb,  if  it  can  remain  unchanged  for  ten  years,  should  not  do  so 
for  a  hundred;  and  if  for  a  hundred,  why  not  for  one  thousand 
years  ?  The  vitality  of  seeds  under  similar  circumstances 
appears  quite  unlimited.  * 

In  the  first  chapter  of  this  treatise,  we  have  ventured  to  assert 
that  light  is  of  more  importance  to  plants  than  air,  although  we 
are  aware  that  this  point  is  open  to  much  discussion,  from  the 
fact  of  some  plants  being  adapted  to  thrive  under  the  almost 
total  deprivation  of  it.  These,  however,  will  generally,  if  not 
solely,  be  found  to  consist  of  plants  in  the  lowest  orders  of 
organization,  such,  for  instance,  as  the  algae,  some  of  which,  pos- 
sessing a  bright  green  color,  have  been  drawn  up  from  the  depth 
of  more  than  one  hundred  fathoms,  to  which  the  sun's  rays  can- 
not penetrate  in  any  appreciable  proportion ;  and  also  the  fungi, 
which  have  been  found  growing  in  caverns  and  mines  to  which 
no  rays  from  the  sun,  either  direct  or  reflected,  would  seem  to 
have  access.  These  facts,  however,  do  not  greatly  affect  the 

*  Melon  seeds  have  been  known  to  grow  at  the  age  of  40  years,  kid- 
ney beans  at  100,  sensitive  plant  at  60,  rye  at  40,  and  there  are  now- 
growing,  in  the  garden  of  the  Horticultural  Society,  raspberry  plants 
raised  from  seeds  1600  or  1700  years  old.  —  [Lindley's  Introduction  to- 
Botany.] 


250  PRINCIPLES    OF   VENTILATION. 

accuracy  of  our  assertion,  for  we  find  that  all  the  highly  devel- 
oped organisms,  such  as  we  cultivate  in  our  hot-houses,  are  only 
adapted  to  exist  where  they  can  be  daily  invigorated  by  the 
sun's  rays.  This  fact  is  very  strikingly  illustrated  in  the  effect 
produced  on  tropical  plants  growing  in  hot-houses  in  the  north- 
ern latitudes,  where,  deprived  of  the  intensity  of  the  sun's  rays, 
under  which  they  naturally  luxuriate,  they  seem  completely 
changed  by  the  long  absence  of  the  luminary  on.  whose  cheering 
influence  they  depend.  In  such  cases,  no  quantity  or  quality 
of  air  will  compensate  for  the  loss  of  the  sun's  vivifying  beams. 
In  the  management  of  hot-house  plants,  the  attentive  ob- 
server cannot  fail  to  perceive  the  remarkable  effects  produced 
upon  certain  kinds  of  plants  by  the  circumstances  in  which  they 
are  placed,  as  to  heat,  light,  and  air;  and  hence  the  propriety  of 
arranging  plants  in  hot-houses,  not  merely  according  to  their 
heights  and  colors,  but  also  according  to  their  habits  and 
requirements  in  relation  to  these  elements.^  Some  plants  will 
endure  an  intensity  of  solar  light,  without  injury,  which  would 
utterly  paralyze  and  suspend  the  functions  of  others ;  some  will 
luxuriate  in  an  arid  temperature,  in  which  others  would  be 
destroyed,  and  some  require  daily  supplies  of  fresh  air,  while 
others  will  exist  even  in  a  healthy  state  for  years  where  the 
atmospheric  air  is,  one  would  think,  almost  excluded.  Even 
in  nature  there  are  many  striking  exemplifications  of  these 
facts.  A  hot  spring  in  Manilla  islands,  which  raises  the  ther- 
mometer to  187°,  has  plants  flourishing  in  it  and  on  its  bor- 
ders. In  hot  springs  near  a  river  of  Louisiana,  the  tempera- 
ture of  which  is  from  122°  to  146°,  have  been  seen  growing,  not 
merely  the  lower  and  simpler  plants,  but  shrubs  and  trees.  In 
one  of  the  Geysers  of  Iceland,  which  was  hot  enough  to  boil  an 

*  For  example,  the  common  weeds,  called  chickweed,  groundsel  and 
Poa  annua.,  evidently  grow  at  a  temperature  very  near  that  of  32°, 
while  the  nettles,  and  mallows,  and  other  weeds  around  them,  remain 
torpid.  In  like  manner,  while  our  native  trees  are  suited  to  bear  the 
low  temperature  of  an  English  summer,  and,  in  most  cases,  suffer 
if  removed  into  a  warmer  country,  such  plants  as  the  mango  and  coffee- 
tree,  etc.,  inhabitants  of  tropical  countries,  soon  perish,  even  in  our 
warmest  weather,  if  exposed  to  the  open  air.  —  [Lind.  The.  of  Hort.] 


PRINCIPLES    OF    VENTILATION.  251 

egg  in  four  mmutes,  a  species  of  chara  has  been  found  growing 
and  reproducing  itself;  and  vegetation  of  an  humble  kind  has 
been  observed  in  the  similar  boiling  springs  of  Arabia,  and  the 
Cape  of  Good  Hope.  One  of  the  most  remarkable  facts  on 
record,  in  reference  to  the  power  of  vegetation  to  proceed  under 
a  high  temperature,  is  related  by  Sir  G.  Staunton,  in  his  account 
of  Lord  Macartney's  Embassy  to  China.  At  the  island  of 
Amsterdam  a  spring  was  found,  the  mud  of  which  was  far  hot- 
ter than  boiling  water,  and  gave  birth  to  a  species  of  liverwort. 
A  large  squill  bulb,  which  it  was  wished  to  dry  and  preserve, 
has  been  known  to  push  up  its  stalk  and  leaves,  when  buried  in 
sand  kept  up  to  a  temperature  much  exceeding  that  of  boiling 
water. 

Again,  we  have  observed  plants  exceedingly  tenacious  of  life 
under  the  deleterious  influences  of  carbonic  acid,  sulphureous, 
chlorine  arid  other  gases.  We  have  seen  a  number  of  different 
kinds  of  plants  placed  in  a  close  frame,  and  fumigated  with  sul- 
phureous gas,  the  greater  part  of  which  were  destroyed,  though 
a  few  of  them  were  uninjured.  This  fact  has  been  observed  by 
many  in  the  fumigating  of  their  green-houses  with  tobacco,  when 
some  of  the  tender  sorts  would  be  sensibly  injured  by  the  smoke, 
while  others,  though  receiving  a  much  larger  portion,  bore  it 
with  impunity. 

It  is  evident,  however,  that  though  many  plants  will  live  for 
a  short  time  under  these  circumstances,  a  certain  condition  of 
the  atmosphere,  as  well  as  a  given  amount  of  light  and  heat,  is 
necessary  to  the  performance  of  their  functions,  and  the  perfec- 
tion of  their  flowers  and  fruit.  The  fact  is  well  known,  that  if 
we  take  a  healthy  plant  from  the  light  and  airy  green-house,  and 
place  it  in  the  room  of  a  dwelling-house,  it  will  become  sickly, 
and  ultimately  languish  and  die ;  if  it  be  placed  in  a  dark,  cold 
cellar,  its  death  will  be  more  speedily  produced.  In  like  man- 
ner, roses  grown  in  a  forcing-house  in  winter  are  less  fragrant 
than  those  grown  in  the  warm  sunshine  of  summer.  In  gen- 
eral, plants  grown  in  the  summer  months  form  secretions  more 
active,  in  every  respect,  than  the  same  kind  of  plants  grown  in  a 
hot-house,  under  the  clouded  skies  of  winter ;  and  even  in  our 
finest  forced  fruits  and  vegetables  this  is  perceptibly  the  case. 
22 


PRINCIPLES   OF   VENTILATION. 

2.  Much  discussion  has  taken  place  upon  the  question 
whether  or  not  vegetation  is,  upon  the  whole,  serviceable  in  puri- 
fying the  atmosphere ;  that  is,  whether  plants  give  out  most  car- 
bonic acid  or  most  oxygen.  Priestley  maintained  that  the  latter 
was  the  only  effect  of  vegetation,  and  that  plants  and  animals 
are  thus  constantly  effecting  changes  in  the  atmosphere  which 
counterbalance  one  another.  Subsequent  experiments  seem  to 
show,  however,  that  the  carbonic  acid  given  out  during  the 
night,  equals  or  even  exceeds  in  amount  the  oxygen  given  out 
by  day.  But  this  might  be  owing  to  the  employment  of  plants 
which  had  become  weak  and  unhealthy,  by  being  kept  in  an 
impure  atmosphere,  previous  to  being  experimented  on,  and 
which  had  not  been  exposed  to  a  fair  degree  of  light.  Dr.  Dau- 
beny,  of  Oxford,  has  recently  shown  that,  in  fine  weather,  a 
plant,  consisting  chiefly  of  leaves  and  stems,  if  confined  in  a 
capacious  vessel,  and  duly  supplied  with  carbonic  acid  during 
sunshine,  as  fast  as  it  removes  it,  will  go  on  adding  to  the  pro- 
portion of  oxygen  present  so  long  as  it  continues  healthy; 
the  slight  diminution  of  oxygen  and  increase  of  carbonic  acid 
which  take  place  during  the  night  bearing  no  considerable  pro- 
portion to  the  degree  in  which  the  contrary  effect  occurs  during 
the  day/* 

Thus  we  see  that  the  two  great  organized  kingdoms  of 
nature  are  made  to  cooperate  in  the  execution  of  the  same 
design,  each  ministering  to  the  other,  and  preserving  that  due 
balance  in  the  constitution  of  the  atmosphere,  which  adapts  it 
to  the  welfare  and  activity  of  every  order  of  beings,  and  which 
is  quickly  destroyed  when  the  operations  of  any  of  them  become 

*  Plants  decompose  carbonic  acid  during  the  day,  and  form  it  again 
during  the  night,  —  the  oxygen  they  inhale  at  that  time  entering  again 
into  combination  with  their  carbon,  —  and,  during  the  healthy  state  of  a 
plant,  the  decomposition  by  day,  and  recomposition  by  night,  of  this 
gaseous  matter,  are  perpetually  going  on.  The  quantity  of  carbonic  acid 
decomposed  is  in  proportion  to  the  intensity  of  the  light  which  strikes  a 
leaf,  the  smallest  amount  being  in  shady  places  ;  and  the  healthiness  of 
a  plant  is  cateris  paribus  in  proportion  to  the  quantity  of  carbonic  acid 
decomposed.  Therefore,  the  healthiness  of  a  plant  should  be  in  propor- 
tion to  the  quantity  of  light  it  receives  by  day.  —  [Lind.  The.  of  Hort.] 


PRINCIPLES   OF    VENTILATION.  253 

suspended,  as  is  the  case  in  the  artificial  atmosphere  of  a  hot- 
house. And  as  by  artificial  means  the  balance  is  therein 
destroyed,  so,  also,  by  artificial  means  must  the  elements  of  the 
atmosphere  be  adjusted,  and  the  balance  maintained. 

It  is  impossible  for  us  to  contemplate  so  special  an  adjustment 
of  opposite  effects,  without  admiring  this  beautiful  dispensation 
of  Providence,  extending  over  so  vast  a  scale  of  being,  and 
demonstrating  the  unity  of  the  plan  upon  which  the  whole  sys- 
tem of  the  organized  creation  is  designed.  And  yet  man,  in 
his  ignorance,  has  done  his  utmost  to  destroy  this  beautiful  and 
harmonious  plan.  It  was  evidently  the  intention  of  the  Creator, 
that  animal  and  vegetable  life  should  everywhere  exist  together, 
so  that  the  baneful  influence  which  the  former  is  constantly 
exercising  upon  the  air  should  be  counteracted  by  the  latter. 
Nothing,  therefore,  can  be  more  prejudicial  to  the  health  of  a 
large  population,  than  the  close  packing  of  houses  together,  as 
presented  in  large  cities.  Hundreds  of  thousands  of  men,  with 
manufactories  of  all  kinds,  —  the  smoke  and  vapors  of  which  are 
still  more  injurious  than  the  foul  air  produced  by  human  respi- 
ration,—  being  crowded  together  in  the  smallest  possible  com- 
pass, with  scarcely  the  intervention  of  an  open  space  on  which  the 
light  and  air  of  heaven  may  freely  play,  and  without  any  oppor- 
tunity for  the  growth  of  any  kind  of  vegetation  sufficiently  luxu- 
riant to  give  pleasure  to  the  eye,  or  sufficiently  energetic  to 
answer  its  natural  purpose ;  for  the  close  confined  atmosphere 
of  crowded  cities  is  almost  as  injurious  to  vegetation  as  to  ani- 
mals; the  smoke,  which  is  constantly  hovering  above  them 
prevents  their  enjoyment  of  the  clear  bright  sunshine  which 
they  require  for  their  health,  and  the  dust,  which  is  constantly 
floating  in  the  atmosphere,  covers  the  surface  of  their  leaves, 
clogs  up  the  pores,  and  prevents  respiration. 

This  is  the  reason  why  plants  thrive  so  badly  in  dwelling- 
houses  in  large  cities,  and  also  in  the  external  air  in  the  streets 
and  squares.  But  lofty  trees  are  so  beneficial  in  such  situations 
that  they  have  with  truth  been  called  the  lungs  of  large  cities, 
so  important  is  the  effect  produced  by  them  in  purifying  the  air. 
It  is  true,  they  may  occasion  some  degree  of  dampness  in  the 
immediate  neighborhood,  but  this  evil  is  more  than  counterbal- 


254  PRINCIPLES   OF   VENTILATION. 

anced  by  the  good  they  effect.  "  New  Haven,"  justly  called  the 
City  of  Elms,  is  almost  embowered  in  the  shade  of  lofty  trees, 
and  is  remarkable  for  the  salubrity  of  its  atmosphere,  and  the 
health  of  its  inhabitants.  There,  almost  every  house  has  its 
garden  ;  and  the  daily  consumers  of  its  deleterious  exhalations 
stand  in  the  open  streets,  at  once  the  ornaments  of  the  city  and 
the  scavengers  of  the  air.  The  cutting  down  of  a  healthy  tree, 
in  the  midst  of  a  large  town,  without  some  very  strong  reason, 
should  be  regarded  as  an  offence  to  the  community,  and  an 
injury  to  the  public  weal.  It  is  much  to  be  wished  that  other 
towns,  that  are  rapidly  increasing  in  extent  and  population, 
would  follow  the  example  of  New  Haven,  and  bad  ventilation 
and  impure  air  would,  in  a  very  great  degree,  be  deprived  of 
their  injurious  effects. 

2.  Under  favorable  circumstances,  plants  are  able  to  appropriate 
a  larger  amount  of  carbonic  acid  than  that  commonly  existing 
in  the  atmosphere.  The  vegetation  around  the  springs,  in  the 
valley  of  Gottingen,  which  abound  in  carbonic  acid,  is  very  rich 
and  luxuriant,  appearing  several  weeks  earlier  in  spring,  and 
continuing  much  later  in  autumn,  than  at  other  spots  in  the 
same  district.  But  it  is  probable  that,  taking  the  average  of  the 
whole  globe,  and  at  all  seasons,  the  quantity  of  carbonic  acid 
existing  in  the  air  is  that  most  adapted  to  maintain  the  health 
of  the  plants  at  present  inhabitants  on  its  surface,  as  well  as  to 
interfere  as  little  as  possible  with  the  animal  creation.  In  hot- 
houses, however,  the  case  is  different,  especially  in  winter  ;  for, 
although  carbonic  acid  be  not  produced  by  the  respiration  of 
animals,  it  is  produced  in  abundance  by  other  causes,  and  these 
same  causes  also  depriving  the  atmosphere  of  oxygen  and  its 
aqueous  vapor,  the  carbonic  remains  in  excess,  and  its  effect 
upon  the  plants  is  easily  perceived.  The  presence  of  oxygen, 
in  proper  quantity,  in  the  atmosphere  of  a  green-house,  or  hot- 
house of  any  kind,  is  even  more  necessary  to  be  artificially 
maintained,  than  carbonic  acid,  because  the  oxygen  affords  the 
means  by  which  the  superfluous  carbon  is  removed.  We  know 
that  plants  in  a  hot-house  suffer  more  frequently  from  an  excess 
of  carbon  than  an  excess  of  oxygen,  arising  from  the  causes 


PRINCIPLES    OF   VENTILATION. 


above  stated.  It  has  been  calculated  that  hot-houses,  during  the 
application  of  fire  heat,  contain  four  times  as  much  carbonic 
acid  in  their  atmosphere  as  is  necessary  for  the  health  of  the 
plants. 

"  Charcoal  possesses  the  property  of  absorbing  some  gases  to  a 
great  extent,  as  may  be  seen  by  the  following  table,  in  which 
the  numbers  indicate  the  volumes  of  gases  absorbed,  that  of  the 
charcoal  being  taken  as  unity.1* 

Absorption  of  Gases  by  Charcoal. 


Ammonia, 90 

Muriatic  acid, 85 

Sulphureous  acid, 65 

Sulphuretted  hydrogen,  ....  55 

Nitrous  oxide, 40 

Carbonic  acid, 35 


Bi-carb.  hydrogen, 35 

Carbonic  oxide, 9.4 

Oxygen, 9.2 

Nitrogen, 7.5 

Carbur.  hydrogen, 5 

Hydrogen, 1.7" 


The  above  table  will  show  how  very  useful  charcoal  may  be 
rendered  as  an  agent  in  the  absorption  of  these  gases,  when 
present  in  excess,  either  in  a  plant-house  or  other  places. 

3.  The  evolution  of  heat  by  plants  is  most  evident  at  those 
periods  of  their  existence  in  which  an  extraordinary  quantity  of 
carbonic  acid  is  formed  and  given  off.  This  is  the  case  during 
the  germination  of  seeds ;  and  though  the  heat  produced  by  a 
single  seed  is  too  soon  carried  off  by  surrounding  bodies  to  be 
perceptible,  it  accumulates  to  a  high  degree,  where  a  number 
are  brought  together,  as  in  the  process  of  malting,  when  the 
thermometer  has  been  seen  to  rise  110°.  An  extraordinary 
amount  of  carbonic  acid  has  been  found  to  accumulate  in  a  hot- 
house, in  one  night,  so  as  sensibly  to  affect  the  respiration  of  in- 
dividuals entering  the  house  in  the  morning ;  which  shows  the 
necessity  of  night  ventilation.  The  disengagement  of  carbonic 
acid  has  been  sensibly  found  in  some  plants,  by  the  evolution 
of  heat  in  some  of  their  organs.  Thus,  the  flower  of  a  gera- 
nium has  been  found  to  possess  a  heat  of  87°,  when  the  air 
around  it  was  81°.  As  in  the  case  of  seeds,  however,  the  pro- 
duction of  heat  is  most  sensible  where  the  flowers  are  crowded 
together,  and  in  those  flowers  where  the  size  of  the  fleshy  disk  is 


22*  *  Daniel's  Introduction  to  Chemistry. 


256  PRINCIPLES    OF    VENTILATION. 

most  considerable,  the  quantity  of  carbon  to  be  united  with  the 
oxygen  is  consequently  the  greatest.  And  the  combination  of 
this  cause  with  the  other,  causes  the  temperature  of  the  clus- 
ters to  be  raised  very  high.  A  thermometer  placed  in  the 
centre  of  five  spadices  has  been  seen  to  rise  to  111°,  and  one  in 
the  centre  of  twelve,  to  121°,  while  the  temperature  of  the  ex- 
ternal one  was  only  66°. 

From  what  has  been  stated,  we  think  it  may  be  argued  that 
plant-houses  require  to  be  ventilated  at  night  even  more  than 
during  the  day ;  but  the  quantity  of  air  then  admitted  must 
be  in  proportion  to  the  mean  of  the  internal  and  external 
temperatures;  but  more  particularly  depending  on  the  con- 
dition of  the  plants. 

4.  Various  theories  have  been  propounded  by  physiologists 
regarding  the  power  of  plants  to  withstand  vicissitudes  of  tem- 
perature, and,  among  others,  we  have  the  following  from  the  high 
authority  of  Decandolle  :  — 

First,  in  the  inverse  ratio  of  the  quantity  of  water  they  con- 
tain ;  secondly,  in  proportion  to  the  viscidity  of  their  fluids ; 
thirdly,  in  the  inverse  ratio  of  the  rapidity  with  which  the  fluids 
circulate ;  fourthly,  in  proportion  to  the  size  of  the  cells,  so  is 
the  liability  of  the  plants  to  freeze ;  fifthly,  the  power  of  plants 
to  resist  the  extremes  of  temperature  is  in  exact  proportion  to 
the  amount  of  confined  air  which  the  structure  of  the  plants 
enables  them  to  contain.  These  and  other  principles  are  laid 
down,  and,  apart  from  their  practical  observation,  they  are  of 
themselves  sufficient  to  form  the  ground  of  theory.  There  is 
nothing,  however,  in  the  above  calculated  to  be  of  material  ser- 
vice to  the  gardener  in  the  culture  of  exotic  plants.  The  dis- 
tinctions upon  which  rest  their  powers  to  resist  changes  of  tem- 
perature are  by  far  too  undefined  and  minute  to  enable  us  to 
determine  the  quantity  or  quality  of  the  organic  elements  they 
contain.  Neither  can  we  ascertain  the  dimensions  of  the  cells 
with  sufficient  accuracy  to  determine  the  precise  degree  of  heat 
or  cold  which  any  given  plant  will  endure.  In  the  management 
of  tender  plants,  we  must  find  a  firmer  foundation  on  which  to 
rest  our  principles  of  action.  We  must  endeavor  to  ground  our 


PRINCIPLES   OF    VENTILATION.  257 

judgment  upon  broader  and  safer  principles ;  and,  in  order  to 
reach  this  point,  let  us  briefly  consider  the  nature  of  atmospheric 
action  upon  hot-houses. 

Before  entering  upon  any  illustration  of  its  practical  effects 
upon  these  structures,  we  will  give  an  extract  from  Dai- 
ton's  Chemical  Philosophy,  which  will  enable  us  to  account 
more  clearly  for  some  of  those  results  that  we  have  often 
observed,  and  which  have  so  often  humiliated  our  practical  pride 
and  baffled  all  our  boasted  experience.  In  fact,  they  have  been 
considered  as  belonging  to  that  class  of  unaccountabilities  which 
our  Creator  has  placed  beyond  the  ken  of  human  discovery. 

"  It  is  a  remarkable  fact,"  Dalton  observes,  "  and  has  never  I 
believe  been  fully  or  satisfactorily  accounted  for,  that  the  atmos- 
phere, in  all  places  and  seasons,  has  been  found  to  decrease  in 
temperature  as  we  ascend,  and  nearly  in  arithmetical  progression. 
Sometimes  this  fact  may  have  been  otherwise,  i.  e.,  that  the  air 
was  colder  at  the  surface  of  the  earth  than  above;  particularly  at 
the  breaking  up  of  a  frost,  I  have  observed  it  so.  But  this  is  evi- 
dently the  effect  of  a  great  a  ad  extraordinary  commotion  in  the 
atmosphere,  and  is  generally  of  very  short  duration.  What, 
then,  is  the  occasion  of  this  diminution  of  temperature  in  ascend- 
ing? Before  this  question  can  be  solved,  it  may  be  necessary 
to  consider  the  defects  of  the  common  solution.  Air,  it  is  said, 
is  not  heated  by  the  direct  rays  of  the  sun,  which  passes  through 
it  as  a  transparent  medium,  without  producing  any  calorific 
effect  till  they  reach  the  surface  of  the  earth.  The  earth,  being 
heated,  communicates  a  portion  to  the  atmosphere,  while  the 
upper  strata,  in  proportion  as  they  are  more  remote,  receive  less 
heat,  forming  a  gradation  of  temperature  similar  to  what  takes 
place  along  a  bar  of  iron,  when  one  of  its  ends  is  heated."  The 
first  part  of  the  above  solution  is  probably  correct.  Air,  it  would 
seem,  is  singular  in  regard  to  heat ;  it  neither  receives  nor  dis- 
charges it,  in  a  radiant  state.  If  so,  the  propagation  of  heat 
through  air  must  be  opposed  by  its  conducting  power,  the  same 
as  in  water.  Now,  we  know  that  heat,  applied  to  the  under  sur- 
face of  a  column  of  water,  is  propagated  upward  with  great 
velocity,  by  the  actual  ascent  of  the  heated  particles  ;  it  is  equally 
certain  that  heated  air  ascends  in  the  same  way.  From  these 


258  PRINCIPLES    OF    VENTILATION. 

observations,  it  would  follow  that  the  causes  assigned  above  for 
the  gradual  changes  of  temperature  in  a  perpendicular  column 
of  atmosphere,  would  apply  to  a  state  of  temperature  the  very 
reverse  of  the  fact ;  namely,  that  the  higher  the  ascent,  or  the 
more  distant  from  the  earth,  the  higher  would  be  the  tempera- 
ture. Whether  this  reasoning  be  correct,  or  not,  we  think  it  must 
be  universally  allowed  that  the  fact  has  not  hitherto  received  a 
very  satisfactory  explanation.  We  conceive  it  to  be  one  involv- 
ing a  new  principle  of  heat ;  by  which  we  mean,  a  principle 
which  no  other  phenomenon  of  nature  presents  us  with,  and 
which  is  not  at  present  recognized  as  such.  We  shall  endeavor, 
in  what  follows,  to  make  out  that  principle. 

The  principle  is  this.  The  natural  equilibrium  of  heat,  in  an 
atmosphere,  is  when  each  atom  of  air,  in  the  same  perpendicular 
column,  is  possessed  of  the  same  quantity  of  heat ;  and,  conse- 
quently, the  natural  equilibrium  of  heat  in  an  atmosphere  is 
when  the  temperature  gradually  diminishes  in  ascending.  That 
this  is  a  just  consequence  cannot  be  denied,  when  we  consider 
that  air  increases,  in  its  capacity  for  heat,  by  rarefaction  ;  and, 
therefore,  if  the  quantity  of  air  be  limited,  it  must  be  regulated 
by  the  density.  It  is  an  established  principle,  that  every  body 
on  the  surface  of  the  earth,  unequally  heated,  is  observed  con- 
stantly to  tend  towards  an  equality.  The  new  principle  an- 
nounced above  would  seem  to  suggest  an  exception  to  this  law ; 
but  if  it  be  thoroughly  examined,  it  can  scarcely  appear  in  that 
light.  Equality  of  heat  and  equality  of  temperature,  when 
applied  to  the  same  body,  in  the  same  state,  are  found  to  be  so 
uniformly  associated  together,  that  we  scarcely  think  of  making 
any  distinction  between  the  two  expressions.  No  one  would 
object  to  the  commonly  observed  law  being  expressed  in  these 
terms.  When  any  body  is  equally  heated,  the  equilibrium  is 
found  to  be  restored,  when  each  particle  of  the  body  becomes 
possessed  of  the  same  quantity  of  heat.  Now  the  law,  thus 
expressed,  is  what  I  apprehend  to  be  the  true  general  law,  which 
applies  to  the  atmosphere  as  well  as  to  other  bodies.  It  is  an 
equality  of  heat,  and  not  an  equality  of  temperature,  that  nature 
tends  to  restore. 

The  atmosphere,  indeed,  presents  to  us  a  strikingly  peculiar 


PRINCIPLES    OF    VENTILATION.  259 

feature,  in  its  regard  to  heat.  We  see,  in  a  perpendicular  col- 
umn of  air,  a  body  without  any  change  of  form,  slowly  and 
gradually  changing  its  capacity  for  heat,  from  a  less  to  a  greater ; 
but  all  other  bodies  retain  a  uniform  capacity  throughout  their 
substance.  If  it  be  asked  why  an  equilibrium  of  heat  should 
turn  upon  the  quality  in  quantity,  rather  than  in  temperature,  I 
answer,  I  do  not  know ;  but  I  rest  the  proof  of  it  upon  the  fact 
of  the  inequality  of  temperature  observed  in  the  atmosphere  in 
ascending,  which  invariably  becomes  colder  as  we  ascend  in 
height ;  while,  in  artificial  atmospheres,  as  in  the  case  of  a  hot- 
house, the  fact  is  quite  the  reverse.  If  the  natural  tendency  of 
air  was  to  an  equality  of  temperature,  there  does  not  appear  to 
me  any  reason  why  the  lower  regions  of  air  are  warmer  than 
the  higher,  or  why  the  law  of  equalization  held  good  in  one  case 
and  not  in  another. 

To  enable  us  to  apply  these  arguments  more  clearly  to  our 
subject,  it  will  be  necessary  more  fully  to  consider  the  relation 
of  the  atmosphere  in  regard  to  heat ;  and  the  arguments  already 
advanced  in  behalf  of  the  principle  we  are  endeavoring  to  estab- 
lish, are  powerfully  corroborated  by  the  following  facts. 

We  find,  by  the  observations  of  Bougeur,  Sassure,  and  Gay 
Lussac,  that  the  temperature  of  the  atmosphere,  at  an  elevation 
where  the  weight  is  half  that  at  the  surface,  (about  14,000  feet, 
or  less  than  three  miles,)  is  reduced  in  temperature  50°  Fahren- 
heit; and,  from  experiment,  it  appears  that  air,  suddenly  rarefied 
from  two  to  one,  produces  50°  of  cold.  Hence  we  might  infer 
that  the  stratum  of  air  at  the  earth's  surface  being  taken  up  to 
the  height  above  mentioned,  preserving  its  original  temperature 
and  suffered  to  expand,  becomes  two  measures,  and  is  reduced  to 
the  temperature  of  the  surrounding  air,  and  vice  versa.  In  like 
manner,  we  may  infer,  if  a  column  of  air  from  the  higher  strata 
of  the  atmosphere  were  condensed  and  brought  into  a  horizon- 
tal position  on  the  earth's  surface,  it  would  become  of  the  same 
density  and  temperature  as  the  air  around  it,  without  receiving 
or  parting  with  any  heat  whatever.  Another  important  argu- 
ment in  favor  of  the  theory  here  advanced,  may  be  derived  from 
the  contemplation  of  an  atmosphere  of  vapor.  Suppose  the  pres- 
ent aerial  atmosphere  were  to  be  substituted  for  one  of  aqueous 


260  PRINCIPLES    OF    VENTILATION. 

vapor ;  and  suppose,  further,  that  the  temperature  of  the  earth's 
surface  were  uniformly  212°,  and  its  weight  equal  to  30  inches 
of  mercury.  Now,  at  the  elevation  of  about  six  miles,  the 
weight  would  be  fifteen  inches,  or  one  half  of  that  below ;  at 
twelve  miles,  it  would  be  7£  inches,  or  one  fourth  of  that  at  the 
surface,  and  the  temperature  would  probably  diminish  25°  at 
each  of  these  intervals.  It  could  not  diminish  more  ;  for  the 
diminution  of  temperature  25°  reduces  the  force  of  vapor  one 
half.  If,  therefore,  a  greater  reduction  of  temperature  were  to 
take  place,  the  weight  of  the  incumbent  atmosphere  would  in- 
crease, being  converted  into  water,  and  the  general  equilibrium 
would  thus  be  disturbed  by  condensation  in  the  upper  regions." 
It  has  been  observed,  that  if  the  ventilators  of  hot-houses  be 
kept  close  during  the  day,  the  internal  temperature  will  rise, 
although  no  artificial  heat  be  applied  ;  from  which  it  has  been 
supposed  that  glass  freely  admits  the  calorific  rays  to  pass 
through  it,  in  their  descent,  but  arrests  it  in  their  upward  progress. 
Professor  Robinson  has  proved  that  glass  freely  transmits  the 
luminous  rays,  but  stops  the  calorific  rays,  till  it  becomes  satu- 
rated with  heat  to  a  certain  degree ;  which  proves,  also,  that 
light  and  heat  are  not  identical,  although  both  obey  the  same 
laws  of  reflection,  refraction,  and  radiation.  Although  heat  may 
arise  from  the  same  source  as  light,  and  possess  a  great  affinity 
to  it,  yet  caloric  possesses  properties  peculiar  to  itself,  and  differs 
in  its  degree  of  affinity  for  other  bodies ;  for,  although  it  has  a 
tendency  to  come  to  an  equilibrium,  when  bodies  differing  in 
quality  are  exposed  to  its  influence,  it  has  been  found  thit 
these  bodies  do  not  all  come  into  an  equal  temperature  at  the 
same  time.  Caloric  readily  enters  into  some  bodies,  and  freely 
combines  with  them,  whereby  their  temperature  becomes  in- 
creased, and  their  properties  sometimes  changed.  [See  Part  I., 
Construction,  sec.  Glass,  p.  106.] 

From  the  foregoing  remarks,  it  will  easily  be  perceived  that 
many  of  our  operations,  in  the  management  of  hot-houses,  are 
not  only  theoretically  wrong,  but  diametrically  opposed  to  the 
laws  of  nature.  Our  methods  of  ventilation  are  wrong  in  prac- 
tice, because  our  notions  are  wrong  in  principle.  We  raise  the 


PRINCIPLES   OF   VENTILATION.  261 

temperature  of  our  houses  by  artificial  means,  and  drive  off  the 
oxygen  and  aqueous  vapor,  without  returning  a  supply.  We 
admit  the  heat  to  escape  through  the  laps  and  fissures  of  the 
glass,  of  which  there  is  always  enough  in  badly  glassed  houses 
to  admit  the  escape  of  one  fourth  the  heat  radiated  in  the  house. 
And,  moreover,  we  allow  one  fourth  more  at  least  to  be  taken 
away  by  direct  radiation  from  the  glass,  so  that  hardly  one  half 
of  the  heat  generated  is  used  for  the  purpose  intended.  And, 
lastly,  we  admit  the  external  air  into  the  house,  to  deprive  the 
atmosphere  of  its  moisture  by  condensation.  Likewise,  in  sum- 
mer, we  admit  the  external  air,  in  Sirocco  currents,  to  sweep 
through  the  house,  carrying  away  the  moisture  daily  by  gal- 
lons; and  which,  if  not  returned  in  equal  abundance,  must 
speedily  prove  injurious  to  the  plants. 


. 
SECTION    II. 

EFFECTS     OF     VENTILATION,     &C. 

1.  The  ventilation  of  hot-houses,  during  winter,  requires  all 
the  skill  which  the  most  experienced  gardener  has  at  command. 
It  is  a  comparatively  easy  matter  to  open  and  shut  the  sashes,  or 
ventilators ;  but  to  do  so  with  benefit  to  the  plants,  at  all  times, 
requires  an  amount  of  skill  which  is  seldom  bestowed  upon  it. 
Admitting  large  quantities  of  cold  air  into  a  house,  many  de- 
grees below  the  internal  atmosphere,  cannot  be  otherwise  than 
injurious  to  the  plants  growing  therein.  It  has  been  calculated 
that  a  volume  of  air,  equal  to  400  cubic  feet,  will  absorb  up- 
wards of  36  gallons  of  water  during  its  rise  from  60  to  90° 
of  temperature ;  or,  in  other  words,  upwards  of  a  gallon  has 
been  absorbed  for  every  degree  of  temperature  above  60°.  This 
will,  in  some  measure,  show  the  propriety  of  keeping  the  walls 
and  floors  of  a  plant-house  continually  saturated  with  moisture, 
especially  during  the  hot  days  of  summer,  as  well  as  of  pre- 
venting currents  of  air  from  sweeping  through  the  house.  We 
have  succeeded,  in  this  way,  in  keeping  the  atmosphere  of  a 
green-house  10  or  15°  below  the  external  temperature,  even 
when,  the  latter  stood  above  90°;  and  almost  every  gardener, 
who  has  paid  attention  to  these  matters,  has  experienced  the 
same  results.  It  is  a  common  error  for  gardeners  to  give  large 
supplies  of  air,  in  sultry  weather ;  but,  as  it  is  a  practical  one, 
and  one  of  long  standing,  it  is  excusable  in  those  who  have  not 
studied  its  effects  attentively. 

By  far  the  larger  number  of  gardeners  attach  great  impor- 
tance to  the  ventilation  of  their  houses  abundantly,  without  per- 
haps sufficiently  considering  the  nature  of  the  plants  they  have 
to  manage ;  and,  as  has  been  justly  enough  said,  by  supposing 
that  plants  require  to  be  treated  like  man  himself.  They  con- 


EFFECTS    OF    VENTILATION.  263 

suit  their  own  feelings,  rather  than  the  principles  of  vegetable 
growth.  There  can  be  no  doubt,  however,  that  the  effect  of 
excessive  ventilation  is  more  frequently  injurious  than  advan- 
tageous; and  that  many  houses,  and  especially  hot-houses, 
would  be  more  skilfully  managed,  if  the  power  of  ventilation 
possessed  by  the  gardener  were  much  diminished. 

Animals  require  a  continual  renovation  of  the  air  that  sur- 
rounds them,  because  they  very  speedily  render  it  impure,  by 
the  carbonic  acid  given  off,  and  the  oxygen  abstracted  by  ani- 
mal respiration.  But  the  reverse  is  what  happens  to  plants. 
They  exhale  oxygen  during  the  day,  and  inhale  the  carbonic  acid 
of  the  atmosphere,  thus  depriving  the  latter  of  that  which 
would  render  it  unfit  for  the  sustenance  of  the  higher  orders 
of  the  animal  kingdom  ;  and,  considering  the  manner  in  which 
glass-houses  of  all  kinds  are  constructed,  the  buoyancy  of  the 
air,  in  all  heated  houses,  would  enable  it  to  escape  in  sufficient 
quantity  to  renew  itself  as  quickly  as  it  can  be  necessary  for 
the  maintenance  of  the  healthy  action  of  the  organs  of  vegetable 
respiration. 

It  is,  therefore,  improbable  that  the  ventilation  of  houses,  in 
which  plants  grow,  is  necessary  to  them,  so  far  as  respiration  is 
concerned.  Indeed,  Mr.  Ward  has  proved  that  many  plants 
will  grow  better  in  confined  air,  than  in  that  which  is  often 
changed.  By  placing  various  kinds  of  plants  in  cases,  —  not, 
indeed,  air-tight,  for  that  is  impossible  with  the  means  applied 
to  the  construction  of  a  glass-house,  but  so  as  to  exclude  as 
much  as  possible  the  admission  of  the  external  air,  —  supplying 
them  with  a  due  quantity  of  water,  and  exposing  them  fully  to 
the  light,  he  has  shown  the  possibility  of  cultivating  them  with- 
out ventilation,  with  much  more  success  than  usually  attends 
glass-house  management. 

2.  In  forcing-houses,  in  particular,  it  will  be  evident  from 
what  is  about  to  follow,  that  ventilation,  under  ordinary  circum- 
stances, in  the  early  spring,  may  be  productive  of  injury  rather 
than  of  benefit.  Many  gardeners  now  admit  air  very  sparingly 
to  their  vineries  during  the  time  that  their  leaves  are  tender 
and  the  fruit  unformed.  Some  excellent  hot-houses  have  no 
23 


264  EFFECTS    OF    VENTILATION. 

provision  at  all  for  ventilation ;  and  we  have  the  direct  testimony 
of  Mr.  Knight,  as  to  the  advantage  of  the  practice  to  many 
cases  to  which  it  has  been  commonly  applied. 

"  It  may  be  objected,"  says  Knight,  "  that  plants  do  not 
thrive,  and  that  the  skins  of  grapes  are  thick,  and  that  other 
fruits  are  without  flavor,  in  crowded  forcing-houses.  But  in 
these,  it  is  probably  light,  rather  than  a  more  rapid  change  of  air, 
that  is  wanting ;  for  in  a  forcing-house,  which  I  have  long  devoted 
to  experiments,  I  employ  but  very  little  fire  heat,  and  never  give 
air  till  the  grapes  are  fully  ripe,  in  the  hottest  and  brightest 
weather,  further  than  is  just  necessary  to  prevent  the  leaves 
from  being  destroyed  by  excess  of  heat.  Yet  this  mode  of 
treatment  does  not  at  all  lessen  the  flavor  of  the  fruit,  nor  ren- 
der the  skins  of  the  grapes  thick.  On  the  contrary,  their  skins 
are  always  moist,  remarkably  thin,  and  very  similar  to  those 
grapes  which  have  ripened  in  the  open  air."  —  [Hort.  Trans.] 

We  have  experienced  the  same  results,  as  those  recorded  by 
Mr.  Knight,  under  similar  treatment,  and  that  too  under  a  more 
powerful  sun.  We  have  pursued  this  method  of  giving  a  very 
limited  supply  of  air,  on  an  extensive  scale,  in  some  large 
graperies  in  Maryland,  and  under  glass  of  the  very  worst  possi- 
ble description.  Yet,  during  one  of  the  hottest  summers  which 
had  been  experienced  for  some  years,  these  vines  grew  beyond 
anything  we  had  ever  seen,  without  any  indication  of  injury  by 
the  sun's  burning  rays.  The  lower  surfaces  of  the  houses,  how- 
ever, were  kept  moist,  by  frequent  sprinkling  with  water  during 
the  day.  Many  large  houses  in  England  are  never  aired, 
except,  perhaps,  a  few  apertures  at  the  top  of  the  house,  which 
are  left  open,  night  and  day,  during  the  summer.  But  in  all 
cases  within  our  knowledge,  water  is  abundantly  supplied  to  the 
atmosphere  from  the  floors  of  the  house. 

3.  The  philosophy  of  this  method  is  easily  perceived.  The 
under  surface  of  the  glass  is  continually  covered  with  a  deposi- 
tion of  the  evaporated  moisture,  which  intercepts  the  calorific 
rays,  and  prevents  them  from  being  concentrated  on  the  leaves, 
from  which  cause  the  leaves  are  scorched  and  burned ;  the 
atmosphere,  at  the  same  time,  undergoing  comparatively  little 
change,  or  admixture  with  the  external  air. 


EFFECTS    OF   VENTILATION.  265 

While,  however,  the  natural  atmosphere  of  a  hot-house  can- 
not be  supposed  to  require  changing,  in  order  to  adapt  it  to  the 
respiration  of  plants,  it  is  to  be  borne  in  mind  that  the  air  of 
hot-houses,  artificially  heated,  may  be  rendered  impure  by  the 
means  employed  to  produce  heat,  as  will  be  seen  from  what  has 
already  been  said  on  the  principles  of  heating,  in  the  preceding 
part  of  this  work.  Sulphuric  acid  gas,  in  variable  quantities, 
escapes  from  brick  flues,  especially  old  and  imperfectly  con- 
structed ones,  and  various  other  unsuspected  sources  of  impu- 
rity, an  infinitely  small  quantity  of  which  is  sufficient  to  con- 
taminate the  air,  in  respect  to  vegetable  life. 

Drs.  Turner  and  Christison  found  that  TTnjui7  of  sulphurous 
acid  gas  destroyed  leaves  in  forty -eight  hours ;  and  similar  effects 
were  observed  from  hydro-chloric  acid  gas.  Chlorine,  ammo- 
nia, and  other  gases  produce  the  same  results,  when  their  pres- 
ence is  altogether  undiscoverable  by  the  olfactory  organs.  We 
also  know  that  the  destructive  properties  of  air,  poisoned  by  cor- 
rosive sublimate,  by  its  being  dissolved  and  evaporated  in  the 
atmosphere  of  a  hot-house,  is  not  appreciable  to  the  senses. 
[See  Chemical  Combinations  in  the  Atmosphere,  sec.  IV.,  for 
detailed  information  on  this  subject.] 

Ventilation  is  necessary,  then,  not  to  enable  plants  to  exercise 
their  respiratory  functions,  provided  the  atmospheric  air  is  un- 
mixed with  accidental  impurities,  but  to  carry  off  noxious  vapors 
generated  in  the  atmosphere  of  a  glazed  house,  and  to  produce 
dryness,  or  cold,  or  both.  Thus  it  is  evident  that  air  is  given 
under  many  conditions,  when  it  is  not  only  unnecessary,  but 
injurious. 

When  air  is  admitted,  to  produce  cold  in  the  house,  the 
external  temperature  must  be  lower  than  the  atmosphere  of  the 
house.  This  effect,  however,  cannot  always  be  produced  by 
ventilation,  as,  in  summer,  if  the  houses  be  rightly  managed,  the 
reverse  effect  will  be  produced,  as  the  external  air  is  not  only 
warmer  but  more  drying  in  its  nature  than  the  air  of  the 
house  ought  to  be ;  therefore  its  admission  can  only  prove  inju- 
rious, rather  than  otherwise,  as  we  shall  afterwards  show.  On 
the  other  hand,  if  the  external  air  be  cold,  its  admission  will 


266  EFFECTS    OF    VENTILATION. 

produce  dryness,  which  may  also  prove  injurious  under  certain 
circumstances. 

4.  When  the  external  air  is  admitted  into  a  glazed  house, 
below  the  temperature  of  the  air  it  contains,  the  heated  moist 
air  rushes  out  at  the  upper  ventilators;  or,  if  it  cannot  find 
egress,  it  is  quickly  condensed  upon  the  cold  surface,  against 
which  it  is  forced  to  ascend  ;  the  latter  rapidly  abstracts  from 
the  plants,  etc.,  a  part  of  their  moisture,  and  thus  gives  a  shock 
to  their  constitution  which  cannot  fail  to  be  injurious. 

This  abstraction  of  moisture  is  in  proportion  to  the  rapidity 
of  motion  in  the  air.  But  it  is  not  merely  dryness  that  is  thus 
produced,  or  such  a  lowering  of  the  temperature  as  the  ther- 
mometer suspended  in  the  house  may  indicate.  The  rapid  evapo- 
ration that  takes  place,  upon  the  admission  of  the  air,  produces  a 
degree  of  cold  upon  the  surface  of  the  leaves,  and  of  the  pots  in 
which  they  grow,  as  well  as  all  other  bodies  around  them,  of 
which  our  instruments  give  no  indication.  To  counteract  these 
mischievous  effects,  many  contrivances  have  been  proposed,  in 
order  to  insure  the  introduction  of  fresh  air,  warm  and  loaded 
with  moisture ;  such  as  compelling  the  fresh  air  to  enter  a  house, 
after  passing  through  pipes  moderately  heated,  or  over  hot-water 
pipes  surrounded  by  a  damp  atmosphere,  which  have  been  proved 
decidedly  advantageous,  and  to  which  we  will  subsequently 
refer. 

If  ventilation  is  merely  employed  for  the  purpose  of  purifying 
the  air,  «.  £>,,  for  carrying  off  extraneous  gases  and  vapors  that 
may  be  generated  by  artificial  heat,  it  should  be  introduced,  by 
all  means,  with  great  caution ;  and  some  expedient  should  be 
adopted  for  supplying  it  with  moisture,  as  well  as  to  warm  it 
slightly  on  its  passage  inwards,  more  especially  in  cold,  frosty, 
or  windy  weather. 

If  it  is  only  introduced  for  the  purpose  of  lowering  the  tem- 
perature, as  in  mild  and  genial  spring  and  summer  weather,  it 
may  be  admitted  without  any  such  precaution ;  and  the  freedom 
of  admission  should  be  in  proportion  as  the  external  and  inter- 
nal temperatures  approach  each  other  in  equality. 

In  hot,  sultry  weather,  air  should  be  sparingly  admitted,  as 


EFFECTS   OF   VENTILATION.  267 

the  same  effects  are  produced  by  the  excessive  evaporation  as 
by  the  currents  of  cold  air,  as  will  be  afterwards  shown. 

5.  Ventilation  is  also  required,  in  winter,  in  pits  and  frames 
where  soft  and  succulent  plants  are  grown,  especially  in  pits  and 
frames  warmed  with  fermenting  materials.     In  this  case,  much 
care  and  caution  are  necessary ;  the  object  here  being  to  carry  off 
the  superfluous  moisture,  in  order  that  the  succulent  tissue  of 
the  plants  may  not  absorb  more  aqueous  matter  than  they  can 
decompose  and  assimilate.     Although  these  kinds  of  plants  will 
bear  a  high  degree  of  atmospherical  moisture  in  summer,  when 
the  days  are  long  and  the  sun  bright,  and  when,  consequently, 
all  their  digestive  energies  are  in  full   activity,  yet  they  are 
by  no  means  able  to  endure  the  same  amount  in  the  dark,  short 
days  of  winter,  when  their  powers  of  decomposition,  or  diges- 
tion, are  comparatively  feeble. 

6.  The  thermometric  changes  are  by  no  means  satisfactory 
guides  for  regulating  the  admission  of  air  in  hot-houses,  as  the 
effect  required  by  the  indications  of  the  thermometer  may  be 
produced  without  resorting  to  the  admission  of  air.     In  hot- 
houses, we   have  full  control  over  the  state  of  the  atmosphere, 
both  as  regards  its  moisture  and  temperature ;  and  the  means 
of  exercising  this  power  ought  to  be  known  and  familiar  to 
every  gardener.       But   there  are  many  circumstances  which 
ought  to  be  duly  considered  in  the  exercise  of  this  power,  and 
some  unsuspected  results  arise  from  the  unlimited  use  and  exer- 
cise of  it ;    and,  as  has  been  already  said,  by  far  the  greater 
number  of  gardeners  attach  too  much  importance  to  the  mere 
opening  and  shutting  of  sashes,  windows,  etc.,  without  duly 
studying  the  rationale  of  the  practice.     We  will  show  that  the 
practical  effects  of  ventilation  are  not  only  different  from  what 
many  suppose,  but  are  actually  injurious. 

During  winter  we  are  in  the  habit  of  raising  the  temperature 
of  our  hot-houses,  by  artificial  heat,  to  45  or  50°  ;  then,  for  six 
or  seven  hours  during  the  day,  we  open  the  lights  and  admit  a 
large  quantity  of  cold  air.  This  is  also  a  stumbliag-block,  on 
which  a  great  many  gardeners  fall ;  for  it  is  not  solely  to  the 
23* 


268  EFFECTS    OF    VENTILATION. 

temperature,  but  rather  to  the  hygrometrical  state  of  the  atmos- 
phere, we  ought  to  look.  We  ought  to  regulate  the  admission 
of  air,  not  solely  by  the  thermometer,  but  also  by  the  hygrome- 
ter ;  for,  upon  the  latter  condition,  the  health  of  the  plants,  and 
the  perfection  of  their  flowers  and  fruit,  very  much  depend ;  — 
and,  consequently,  it  is  a  matter  which  ought  to  be  studiously 
considered.  Nothing  is  more  injurious  than  the  admission  of 
currents  of  air  when  the  external  temperature  is  lower  than  the 
internal  one ;  and  more  especially  so  to  plants  that  have  been 
for  a  considerable  time  subjected  to  a  high  temperature  by  arti- 
ficial heat. 

The  causes  which  operate  in  rendering  the  atmosphere  of 
hot-houses  unnaturally  arid  may  be  said  to  be  two-fold.  The 
first  is  the  condensation  of  moisture  upon  the  glass,  arising 
from  the  action  of  the  external  cold  upon  its  upper  surface.  The 
second  is  the  escape  of  heated  air  through  the  laps  and  crev- 
ices of  the  glass,  and  otherwise.  This  heated  air  escaping,  car- 
ries along  with  it  a  large  quantity  of  contained  moisture,  the 
loss  of  air  being  supplied  with  cold,  dry  air,  which  finds  access 
by  the  same  means.  The  loss  of  heat  and  moisture  sustained 
by  these  means  is  far  more  than  would  be  supposed  by  those 
who  have  not  calculated  the  amount. 

7.  We  have  seen  that  the  quantity  of  moisture  a  cubic  foot 
of  air  will  hold  in  invisible  suspension  depends  on  its  tem- 
perature ;  and  as  the  temperature  is  increased,  so  is  its  capacity 
for  moisture.  Suppose,  then,  that  this  capacity  is  doubled 
between  the  temperature  of  40  and  60°  ;  that  is  to  say,  every 
cubic  foot  of  air  that  enters  the  house  at  40°,  and  escapes  at  60°, 
carries  with  it  just  double  the  quantity  of  moisture  it  brought  in. 
Now,  every  one  must  be  sensible  that  these  circumstances,  con- 
tinued for  any  length  of  time,  must  render  the  atmosphere  of 
the  house  too  arid  for  healthy  vegetation  ;  and,  consequently,  if 
the  deficiency  of  moisture  so  occasioned  be  not  supplied  by 
artificial  evaporation,  then  the  plants  must  part  with  their  secre- 
tions to  supply  the  atmospheric  demand,  and  the  soil  and  other 
materials  in  the  house  will  also  be  drained  of  their  moisture,  to 
make  up  the  deficiency.  The  .greater  the  difference  between 


EFFECTS    OF    VENTILATION.  269 

the  internal  and  external  temperature,  the  greater  will  be  the 
demand  for  moisture.  Thus,  if  the  external  air  be  at  the  freez- 
ing point,  (32°,)  and  the  air  in  the  house  heated  to  50  degrees, 
then  there  is  three  times  more  moisture  carried  away  by  escap- 
ing air  than  is  brought  in  by  the  returning  quantity;  and, 
escaping  at  90°,  it  carries  away  four  times  as  much,  and  so  on, 
in  proportion  to  the  difference  of  the  two  atmospheres ;  the  ex- 
ternal air,  however,  increasing  in  ratio  as  it  decreases  in  tem- 
perature. 

According  to  these  calculations,  atmospheric  air,  entering  a 
house  at  32°,  and  escaping  at  100°,  carries  away  nearly  six 
times  as  much  moisture  as  it  brings  in.  This,  in  a  short  time, 
would  render  the  atmosphere  of  a  house  deleterious  to  either 
animal  or  vegetable  life  ;  and  in  large  and  lofty  houses  this  is 
practically  the  case.  We  have  managed  a  lofty  plant-house, 
where  the  plants  on  the  side  shelves  were  nearly  frozen,  while  the 
thermometer,  hung  in  the  angle  of  the  roof,  about  45  feet  high, 
stood  at  100  degrees.  Now  this  heated  air,  escaping  at  the  top 
of  the  roof,  as  is  generally  the  case  as  well  as  here,  carried  away 
more  moisture  than  the  small  evaporating  surface  could  supply ; 
the  effects  were,  consequently,  ruinous  to  the  plants.  However 
imperfect  the  above  calculations  may  be,  they  are  within  the 
bounds  of  truth,  and  are  sufficiently  accurate  to  show  the  im- 
portance of  this  subject  to  exotic  horticulture  ;  and  it  will  more 
effectually  impress  upon  our  minds  the  amount  of  care  and  con- 
sideration which  the  ventilating  of  hot-houses  demands.  If  air 
must  be  admitted,  for  the  purpose  of  regulating  the  internal 
temperature,  every  precaution  should  be  taken  to  prevent  it 
from  entering  in  strong  currents,  and  it  should  be  taken  in  from 
the  warmest  side  of  the  house,  and,  if  possible,  over  a  warm 
surface,  —  as  hot-water  pipes,  or  whatever  heating  apparatus  may 
be  employed, —  so  that  the  internal  atmosphere  may  be  gradually 
reduced ;  and,  at  the  same  time,  the  utmost  precaution  should 
be  used  to  prevent  the  escape  of  heated  air,  at  least  as  little  as 
possible,  by  direct  ascension  ;  this  is  easily  accomplished  by  the 
improved  methods  of  ventilation  now  adopted,  some  of  which  I 
shall  hereafter  endeavor  to  describe.  Thus  the  cultivator  is 
enabled  to  modify  the  two  atmospheres,  previous  to  their  com- 


270  EFFECTS    OF   VENTILATION. 

bination,  and  by  raising  the  humidity  in  the  atmosphere  of  the 
house,  to  compensate  for  that  carried  away  by  the  egress  of 
heated  air,  the  plants  will  breathe  an  atmosphere  more  con- 
ducive to  their  healthy  development,  and  will  be  benefited  by 
the  change. 

8.  Every  gardener  has  observed  the  water  on  the  under  sur- 
face of  the  glass,  in  the  morning,  before  the  sun  has  risen, 
warmed  the  glass,  and  driven  it  off  again,  in  the  form  of  aqueous 
vapor.     This  affords  us  a  good  illustration  of  the  immense  quan- 
tity of  moisture  carried  upwards  by  the  heated  air,  and  depos- 
ited upon  the   glass,  by  condensation.     This   moisture  is,  of 
course,  taken  away  from  the  plants,  and  other  bodies  capable 
of  giving  it  off,  and  is  demanded  by  the  air  as  it  becomes  warm, 
and  capable  of  carrying  a  larger  quantity  than  when  no  fire  was 
applied,  —  or  rather,  when   the  temperature  of  the  house  and 
the  temperature  of  the  external  air  were  alike,  for  in  such  case 
no  condensation  on  the  glass  would  take  place  ;  and,  as  I  have 
remarked,  the  proportion  of  water  deposited  will   be  in  exact 
ratio  to  the  intensity  of  the  external  cold  ;    thus,  the   greater 
the  difference,  the  greater  the  deposition ;  for  then  the  action 
of  the  external  cold  upon  the  upper  surface  of  the  glass  being 
greater,  and  the  two  atmospheres  being  brought  into  more  rapid 
proximity,  the  particles  of  heated  air  are  cooled  as  quickly  as 
they  ascend  to  the  under  surface  of  the  glass ;  they  then  fall  to 
supply  the  place  of  others,  leaving  the  contained  moisture  upon 
the   cooling   surface,  in  the  form  of  dew,  —  the  same  process 
being  repeated  through  the  whole  night,  or  until  an  equality  of 
temperature  is  established ;  the  quantity  thus  deposited  amounts 
to  immense  volumes  of  water. 

9.  Experiments  have  proved  that  each  square  foot  of  glass 
contained  in  the  roof  of  a  hot-house  will  cool  down  1J  cubic 
feet  of  heated  air  per  minute  as  many  degrees  as  the  temper- 
ature of  the  internal  exceeds  that  of  the  external  atmosphere. 
Suppose,  for   instance,  that   the   external   air    stands   at   40°, 
and   that  of  the   house  60° ;    then,  for   every  square  foot  of 
glass  contained  in  the  house,  one  and  one  fourth  cubic  feet  of 


EFFECTS   OF    VENTILATION.  271 

air  will  be  cooled  down  the  20  degrees  ;  thus,  60  minus  40  gives 
the  difference,  which  is  20.  If  the  house  contains  800  square 
feet  of  glass,  presented  to  the  action  of  the  external  atmosphere, 
1000  cubic  feet  of  air  will  lose  20  degrees  of  heat ;  consequent- 
ly, the  moisture  this  air  held  in  invisible  solution,  in  virtue  of 
its  20  degrees  of  temperature,  will  be  condensed  by  the  external 
cold,  and  deposited  on  the  glass ;  and  it  will  also  be  found,  that 
the  greater  the  difference  between  the  external  and  internal 
temperatures,  the  greater  will  be  the  amount  of  condensation. 
The  quantity  of  moisture  abstracted  from  plants,  at  high  tem- 
peratures, is  enormous.  This  fact  is  sufficiently  demonstrated 
in  a  hot  summer  day,  when  the  leaves  of  the  trees  are  wilted, 
and  the  garden  vegetables  flag  and  droop  their  leaves.  The 
earth  gives  out  its  moisture,  and  the  atmosphere  carries  it  away. 
The  same  thing  takes  place  in  hot-houses ;  the  moisture  is  ab- 
stracted by  the  heated  air,  and  is  carried  off  in  the  form  of 
invisible  vapor,  till  its  upward  progress  is  arrested  by  the  glass, 
and  the  cold  again  reduces  it  to  water. 

If  we  take,  for  example,  the  roof  of  a  hot-house,  comprising 
750  superficial  feet  of  glass,  and  calculate  that  every  square  foot 
of  that  glass  will  cool  down  1|  cubic  feet  of  heated  air  36° 
per  minute,  and  calculating  the  internal  temperature  at  65°,  we 
shall  find  that  937  cubic  feet  of  air  will  be  cooled  down  36  de- 
grees per  minute.  Now  air,  saturated  at  the  temperature  of  65 
degrees,  contains  about  6-59  grains  of  water  per  cubic  foot,  and 
at  the  temperature  of  30  degrees,  it  is  saturated  with  2-25 
grains  ;  this  gives  4-34  grains  of  water  lost,  in  condensation  on 
the  glass,  per  minute  ;  or  further,  each  square  foot  of  glass  con- 
denses 1 J  cubic  feet,  or  about  5-42  grains  of  water,  per  minute ; 
and  supposing  the  atmosphere  of  a  house,  such  as  we  have  de- 
scribed, to  be  constantly  supplied  with  moisture,  by  evaporation, 
or  otherwise,  there  would  be  abstracted  from  it  about  £  of  "a  pint 
of  water  per  minute,  which  is  about  12  quarts  per  hour,  or  at 
the  rate  of  nearly  72  gallons  in  24  hours.  This  enormous 
amount  of  water,  evaporated  into  the  atmosphere  of  a  hot-house, 
when  reduced  to  calculation,  and  displayed  in  plain  figures, 
seems  to  startle  the  imagination,  and  looks  very  like  exaggera- 
tion; although  it  is  much  below  the  mark  which,  by  a  more 


272  EFFECTS    OF    VENTILATION. 

accurate  calculation,  it  would  certainly  reach,  yet  the  accuracy 
of  these  calculations  will  appear  sufficiently  obvious  to  any  one 
who  has  paid  studious  attention  to  the  subject.  I  say  studious 
attention,  because  a  person  may  be  tolerably  observant  of  atmos- 
pheric phenomena,  and  yet  not  form  anything  like  an  accurate 
idea  of  this  extraordinary  process  going  on  in  his  presence,  and 
the  effect  thereby  produced  on  the  vegetable  system.  When 
we  enter  a  hot-house,  on  a  cold,  frosty  morning,  after  a  strong 
fire  has  been  kept  up  during  the  night,  we  are  very  apt  to  regard 
the  moisture  condensed  upon  the  lower  surface  of  the  glass 
as  an  evidence  of  a  healthy  atmosphere  and  luxuriant  veg- 
etation ;  and  often  have  I  heard  it  stoutly  asserted,  that  it 
was  merely  the  effect  of  an  excess  of  moisture  in  the  atmos- 
phere of  the  house.  This  may  be  partly  true,  but  the  conclusions 
which  are  drawn  from  the  fact  are  founded  on  misconception, 
that  the  moisture  thus  deposited  on  the  glass  has  already  per- 
formed its  purpose  of  benefit  to  the  plants. 


SECTION   III. 

METHODS     OF     VENTILATION,     &C. 

1.  If  we  admit  the  truth  of  the  foregoing  calculations,  (and 
we  cannot  justly  reject  them,  until  they  are  disproved  by  calcu- 
lations more  accurate,  and  observations  more  extended,)  then 
we  must  acknowledge,  also,  that  the  old  methods  of  ventilating 
hot-houses,  which  are  still  in  common  practice,  are  contrary  to 
what  we  know  to  be  right.     Hence  the  question  arises,  How 
are  these  methods  to  be  improved  ?     Now,  I  would  remark,  that 
the  mere  system  on  which  a  house  may  be  ventilated  is  of  com- 
paratively little  importance,  for  no  method  of  ventilation  will  be 
good,  if  the  atmosphere  be  unskilfully  managed.     Various  plans 
have  been  employed  to  modify  the  influence  of  draughts,  or 
currents  of  air,  many  of  which  can  hardly  be  termed  improve- 
ments, since  the  general  effect  is  the  same  as  by  the  old  method 
of  opening  the  top  and  bottom  sashes,  which  admits  a  current 
to  rise  up  beneath  the  under  surface  of  the  glass,  and,  as  it  pro- 
ceeds towards  the  aperture  made  by  letting  down  the  upper 
sashes,  it  carries  the  ascending  moisture  along  with  it,  without 
in  the  slightest  degree  mixing  with,  or  purifying,  the  volume  of 
atmosphere  contained  in  the  lower  portions  of  the  house. 

2.  It  has  long  been  an  object  among  gardeners  to  obtain  a 
motion  in  the  atmosphere  of  a  hot-house ;  and  to  secure  this, 
even  machinery  has,  in  some  instances,  been  employed,  and, 
under  certain  conditions  of  the  atmosphere,  these  machines  may 
go  on  very  well.     But  subject  to  those  vicissitudes  of  climate, 
so  prevalent  in  many  parts  of  this  continent,  the  consequent 
result  of  their  adoption  is,  a  complete  derangement  of  all  that 
equalizing  regularity  which  they  were  intended  to  secure.     It 
appears  to  us  a  matter  of  considerable  difficulty  to  lay  down  a 
definite  rule,  or  propose  a  particular   system  of  ventilating  a 
house,  since  almost  every  locality  has  some  characteristics  pecu- 


274  METHODS    OF    VENTILATION. 

liar  to  itself.  It  is  true,  the  elements  of  the  atmosphere  may  be 
nearly  the  same  in  one  place  as  in  another ;  but  they  are  influ- 
enced by  various  circumstances,  in  different  localities,  and  hold 
soluble  matters  in  suspension  in  very  different  proportions ;  and 
in  places  much  screened  by  trees,  buildings,  and  similar  objects 
of  shelter  and  obstruction,  air  may  be  admitted  with  greater 
impunity  than  in  situations  exposed  to  wind  from  every  quarter 
of  the  compass,  —  the  latter  condition,  as  a  matter  of  course,  re- 
quiring more  care,  not  only  in  the  adjustment  of  the  apertures 
of  admission,  but  also  in  the  admission  itself.  The  course  of 
the  current  of  air,  by  the  common  methods  of  ventilation,  —  that 
is,  by  opening  the  front,  and  letting  down  the  top  sashes,  —  is  ex- 
ceedingly variable  ;  sometimes  the  actual  motion  created  in  the 
atmosphere  is  little  more  than  a  foot,  or  fourteen  inches,  below 
the  surface  of  the  glass.  This  motion  can  be  easily  determined 
by  holding  the  flame  of  a  candle  in  the  current,  when  the  flame 
will  incline  towards  the  aperture  of  egress  ;  lower  it  gradually 
down,  till  it  assumes  and  maintains  a  perpendicular  position, 
being  no  longer  affected  by  the  current,  the  volume  of  air  being, 
in  fact,  stationary,  except  there  be  some  aperture  of  ingress  else- 
where. We  have  found  this  simple  operation  exceedingly  useful 
in  determining  the  currents  of  air  in  large  houses,  and,  in  most 
cases,  it  seldom  fails  in  giving  an  accurate  indication  of  their 
course. 

However  desirable  a  motion  may  be  in  the  atmosphere  of  a 
hot-house,  —  and  I  do  not  doubt  but  it  is  beneficial,  —  yet  it  is  not 
necessary  that  we  should  run  headlong  either  upon  Scylla  or 
Charybdis.  There  is  a  great  difference  between  a  motion  in 
the  atmosphere  created  by  the  warm  particles  ascending,  and 
being  replaced  by  the  denser  and  colder  air,  and  that  created  by 
a  tornado  sweeping  through  the  house.  The  former  motion  is 
only  perceptible  to  the  eye  of  the  attentive  and  experienced  cul- 
tivator, and  he  can  tell  at  a  glance,  by  the  quivering  of  the 
leaves,  that  they  are  fanned  by  a  gentle  zephyr.  I  am  aware 
that  some  gardeners  have  a  peculiar  fancy  for  seeing  their  plants 
and  vine-leaves  bristling  about  by  a  good  wind,  and  may  be 
very  successful,  too,  in  their  productions;  but  it  cannot  be  as- 
serted that  it  is  compatible  with  a  high  state  of  gardening  skill, 


METHODS    OF    VENTILATION. 


275 


or  with  that  perfection  in  horticulture  at  which  it  is  our  duty  to 
aim ;  inasmuch  as  the  revelations  of  science  are  against  it,  as 
has  already  been  shown,  and  practice  has  hitherto  given  no  evi- 
dence to  prove  it  beneficial  to  tender  plants. 

3.  In  large  and  lofty  structures,  and  especially  in  dome-shaped 
houses,  the  management  of  the  atmosphere  becomes  a  matter 
of  much  more  importance  than  in  small  houses.  During  mild 
and  temperate  weather,  things  may  go  on  very  well,  as  at  such 
times  the  external  air  may  be  allowed  to  circulate  through  the 
house  with  greater  impunity ;  but  during  the  heat  of  summer, 
and  the  cold  of  winter,  the  atmosphere  is  much  more  difficult  to 
equalize.  With  a  frosty  air  externally,  and  the  temperature  at  the 
surface  of  the  earth  down  to  zero,  it  is  impossible  to  maintain  a 
proper  degree  of  temperature,  in  all  parts  of  the  house,  without 
positive  injury  to  those  plants  that  may  be  growing,  or  have 
their  branches  extended  into  the  upper  regions  of  the  house.  In 
fact,  without  the  precaution  of  covering,  or  some  such  expe- 
dient, mischief  is  absolutely  unavoidable.  What  has  already 
been  said,  upon  the  nature  and  properties  of  air,  will  sufficiently 
explain  the  cause ;  and,  although  it  has  been  repeatedly  asserted 
by  theorists,  that  one  part  of  a  house  being  heated  by  radiation, 
from  a  body  radiating  heat,  the  equalizing  law  of  nature  will 
heat  all  parts  of  the  house  to  the  same  temperature,  and  as 
speedily,  too,  yet  we  must  enter  our  decided  protest  against 
the  practical  correctness  of  such  a  statement ;  at  least,  in  our 
own  practice,  we  have  never  found  it  so,  under  any  circumstance, 
or  by  any  system  of  heating.  And  hence,  whatever  the  natural 
law  of  equality  may  be,  the  practical  effects  cannot  be  mistaken, 
or  disputed,  as  far  as  regards  hot-houses.  We  know  that  heated 
bodies  tend  to  an  equality  of  temperature  ;  but,  as  has  been 
already  observed,  air,  of  all  other  bodies,  possesses  peculiar 
properties  in  this  respect  in  regard  to  heat,  and  in  nothing  is  this 
peculiarity  more  strikingly  illustrated  than  in  the  case  under 
consideration. 

4.  With  regard  to  the  motion  of  the  atmosphere  in  a  hot- 
house, we  know  that  the  greater  the  difference  between  the  tem- 
24 


276  METHODS    OF    VENTILATION. 

perature  of  the  air  entering  the  house  and  the  atmosphere  of 
the  house  itself,  the  greater  will  be  the  movement  produced 
among  the  particles.  The  motion  is  in  exact  proportion  to  the 
difference  of  temperature  ;  and  hence  the  necessity  of  admitting 
the  external  air,  in  small  quantities,  when  the  external  ther- 
mometer is  low.  The  slightest  cause  that  disturbs  the  equilib- 
rium of  the  air  produces  a  motion.  It  is  more  sensible  than 
the  most  delicate  balance.  It  is  put  in  motion  by  the  slightest 
inequalities  of  pressure,  and  by  the  smallest  change  of  tempera- 
ture. It  is  speedily  rarefied  by  heat,  and  thereby  rendered 
specifically  lighter  than  the  neighboring  portions,  so  that  it 
descends,  while  colder,  and  consequently  denser,  flows  in,  to  re- 
store the  equilibrium.  It  will  be  easily  seen,  from  the  very 
nature  of  this  law,  that  an  equilibrium  cannot  be  maintained  in 
the  artificial  atmosphere  of  a  hot-house,  since  the  source  of 
radiation  must  necessarily  be  confined  to  too  small  a  surface  to 
equalize  the  ascending  heat;  and,  on  the  other  hand,  the  con- 
densation by  cold  is  too  irregular  throughout  the  heated  vol- 
ume. This  irregularity,  produced  by  its  unequal  action  on 
different  parts  of  the  house,  must  ever  render  it  impossible  to 
obtain  an  equality  of  temperature  throughout  an  atmosphere 
heated  by  artificial  means ;  and  the  larger  the  house,  the  greater 
will  be  the  difficulty  of  maintaining  an  equilibrium  in  its  various 
parts.  So  much  so  is  this  the  case,  that,  as  has  been  already 
stated,  the  difference  has  been  found  to  amount  to  100°. 

"Gaseous  bodies  expand  equally  for  an  equal  increase  of 
temperature,  as  measured  by  the  thermometer.  Gay  Lussac 
showed  that  100  measures  of  atmospheric  air,  heated  from  the 
freezing  to  the  boiling  point,  became  137.5  measures ;  conse- 
quently, the  increase  for  180°  Fahrenheit  is  \^  of  its  bulk. 
Dividing  this  quantity  by  180,  we  find  that  a  given  quantity  of 
dry  air  expands  T^  of  the  volume  it  occupied  at  32°,  for  every 
degree  of  Fahrenheit.  New  experiments  have  been  made  by 
Kudberg,  within  a  few  years,  giving  ¥^T  as  the  ratio  of  expan- 
sion for  one  degree  of  Fahrenheit ;  and  these  results  are  con- 
firmed by  Regnault.  This  last  number  may  be  adopted  as  the 
true  increment. 

"If  we  wish  to  ascertain  the  volume  which  100  cubic  inches 


METHODS    OF    VENTILATION. 


277 


of  a  gas  at  40°  would  occupy  at  80°,  we  must  remember  that  it 
does  not  expand  f£T  of  its  bulk  at  40°  for  each  degree,  but  ¥£T 
of  its  bulk  at  32°.  Now,  491  parts  of  air  at  32°  become  492 
at  33°,  become  493  at  34°,  and  so  on.  Hence  we  can  institute 
a  proportion  between  the  volume  at  40°  and  that  at  80°.  * 

Vol.  at  400.  Volume  at  803.  Cubic  inch.  Cubic  inch. 

491  +  8         :         491-J-48          :  :         100  :  108 

5.  The  annexed  cuts  represent 
an  improved  method  of  ventilating 
lean-to  houses,  and  by  which  the 
Fig.  52. 


Fig.  53. 


Fisr.  51. 


*  Wyman  on  Vent. 


278  METHODS    OF   VENTILATION. 

whole  house  may  be  aired  in  the  space  of  one  minute ;  or  as 
many  houses  as  may  be  in  the  range.  This  is  effected  by  a  rod 
passing  along  the  whole  length  of  the  house.  A  pulley  is  fixed 
immediately  above  each  ventilator,  and  another  placed  opposite 
it  upon  the  rod,  as  shown  in  Fig.  51.  A  piece  of  chain  or  cord 
is  attached  to  the  ventilator  at  one  end ;  and  passing  over  the 
pulley,  as  shown  at  a,  Fig.  52,  is  then  fixed  to  the  pulley  placed 
opposite  it  upon  the  rod.  A  larger  wheel,  or  pulley,  is  fixed  at 
one  end  of  the  rod,  (£,)  to  which  is  attached  a  chain,  connected 
with  a  crank,  situated  within  the  reach  of  a  person  standing  on 
the  floor.  This  crank  is  fixed  on  the  back  wall,  as  seen  at  c, 
Fig.  52. 

From  the  foregoing  cuts  and  description  it  will  be  perceived 
that,  by  giving  the  crank  (d)  a  few  turns,  the  whole  of  the  ven- 
tilators will  be  opened.  The  crank  is  provided  with  a  racket,  so 
that  they  may  be  opened  to  any  distance,  from  half  an  inch  to 
the  full  height. 

The  ventilators  in  the  front  wall  may  be  opened  and  shut  by 
the  same  method,  and  may  be,  for  convenience,  brought  from  the 
outside.  Any  length  of  house,  or  any  number  of  houses,  may 
be  ventilated  at  once  by  this  method,  providing  the  apertures 
are  in  a  straight  line;  their  perpendicular  distance  from  the 
horizontal  shaft  makes  no  difference  in  their  facility  of  working. 
The  pulley  cords  of  the  higher  ones  only  require  to  be  length- 
ened according  to  the  distance,  the  diameter  of  the  wheel  on 
which  the  cord  turns  being  equal  all  along  the  shaft. 

6.  Figures  54  and  55  represent  a  method  of  ventilating 
span-roofed  houses.  It  is  employed  in  the  houses  at  Frogmore, 

Fig.  54. 


METHODS    OF    VENTILATION.  279 

in  England.     Fig.  54  represents  the  end  section  of  the  house, 
with  the  ventilator  in  proportion  to  the  other  parts.     Fig.  55 

Fig.  55. 


shows  the  sectional  view  of  the  ventilator,  enlarged  :  a  a  sue 
openings  of  admission,  and  are  covered  with  lattice-work,  to 
break  the  force  of  the  current  of  ingress ;  b,  the  movable  shut- 
ter, which  regulates  the  admission  to  and  egress  from  the  house. 
It  is  scarcely  necessary  to  observe  that  these  houses  have  been 
ventilated  on  the  most  approved  principles;  and  it  appears 
that  several  advantages  are  gained  by  this  method.  For  in- 
stance, the  current  of  heated  air  is  arrested,  in  its  progress 
outwards,  by  the  depending  glass  at  c  c,  and  is,  in  some  meas- 
ure, thrown  downwards,  preventing  also  the  escape  of  its  con- 
tained moisture.  There  is  no  doubt  this  method  is  very  com- 
mendable for  span-roofed  houses ;  and  one  of  its  advantages  is, 
that  the  house  can  be  aired,  at  any  time,  without  the  plants 
being  saturated  with  rain. 

It  is  very  possible  that  these  compound  systems  of  ventilation 
may  excite  a  smile  from  some  who  have,  all  their  lifetime,  been 
accustomed  to  pull  heavy  sashes  up  and  down  for  the  purpose 
of  giving  air.  But  if  we  include,  in  one  computation,  the 
labor,  the  time,  and  the  advantages  of  giving  a  range  of  houses 
three  or  four  hundred  feet  long,  air  at  the  proper  time,  and  all  at 
the  same  moment,  we  will  find  a  value  in  the  system  worthy  of 
something  more  than  the  mere  smile  of  passive  silence,  which 
is  too  frequently  all  that  is  at  first  accorded  to  such  improve- 
ments. 

In  some  establishments,  instead  of  pulleys,  toothed  wheels  are 
fixed  to  the  shaft,  which  are  made  to  work  in  a  curved  handle 
24* 


280  METHODS    OF   VENTILATION. 

attached  to  the  front  sash  by  means  of  a  hinge.  This  curved 
rod  is  toothed  on  the  lower  side  to  answer  the  wheel,  and  is 
kept  in  its  place  by  an  iron  staple,  having  an  eye  through  which 
the  sash-handle  passes,  as  seen  at  a,  Fig.  56.  A  crank  and  rachet- 


Fig.  56. 


wheel  is  provided,  at  one  end  of  the  shaft,  by  turning  which  the 
sashes  are  simultaneously  opened  and  shut,  to  any  distance. 
This  method  is  simple  and  efficient.  It  has  been  extensively 
carried  out  in  the  unique  assemblage  of  horticultural  buildings 
at  Frogmore ;  and,  as  an  improvement  in  the  modes  of  ventilat- 
ing hot-houses,  is  considered,  by  competent  judges,  the  most 
valuable  contrivance  that  has  been  introduced  during  the  last 
half  century.  By  the  turning  of  a  small  windlass,  (which  any 
child  may  do,)  any  quantity  of  air  may  be  admitted,  and  in- 
creased or  diminished  at  pleasure,  throughout  the  whole  range 
of  buildings. 

The  ventilation  of  forcing-houses,  by  this  compound  method 
of  opening  the  whole  sashes  at  once,  is  very  liable  to  produce 
serious  results,  before  the  person  in  charge  becomes  fully 
acquainted  with  the  management  of  it.  This,  like  many  other 
really  valuable  improvements  in  gardening,  has  been  adopted, — 
bungled  in  the  construction,  —  mismanaged  afterwards,  —  then, 
lo  !  it  is  condemned,  with  all  the  pomp  and  dignity  of  practical 
experience !  The  present  moment  affords  an  ocular  demonstra- 
tion of  this  too  common  fact,  Some  people  suppose,  if  they 
can  only  get  mechanical  contrivances  to  accomplish  certain  ends, 


METHODS   OF    VENTILATION.  281 

that  all  is  right.  It  is  certainly  desirable  to  employ  mechan- 
ical contrivances,  whenever  they  can,  as  in  the  present  case,  be 
applied  advantageously.  But  mechanism  can  never  make  a 
gardener,  inasmuch  as  the  chief  part  of  what  constitutes  a  real 
gardener  springs  from  mental,  not  physical,  activity.  It  is  a 
very  easy  matter  to  open  and  shut  the  ventilators  of  a  hot- 
house ;  but  it  requires  something  more  than  mere  mechanical 
power  to  do  so  with  certain  benefit  to  the  inhabitants  within. 

This  will  be  rendered  clear  by  a  common  illustration.  Let  a 
dwelling-room  be  warmed  to  a  temperature  of  60°  ;  and  suppose 
it  to  be  tolerably  well  filled  with  individuals,  by  the  animal  heat 
and  respiration  of  whom  the  room  by  and  by  becomes  somewhat 
raised  in  temperature,  and  contaminated  in  its  atmosphere. 
Then,  all  at  once,  let  the  windows  be  thrown  open,  and  the  con- 
sequence is  not  only  disagreeable,  but  highly  dangerous,  as  is 
manifest  by  the  murmur  which  very  soon  pervades  the  assem- 
bled party.  Now,  the  case  is  precisely  similar  in  a  hot-house, 
only  with  this  difference,  —  the  unfortunate  plants  cannot  speak 
in  audible  sounds  to  tell  the  injuries  that  are  perpetrated  upon 
them ;  yet  they  bear  a  language,  imprinted  on  their  leaves,  no 
less  truthful,  nor  less  understood  by  the  attentive  observer.  The 
above  common  occurrence  is  a  plain  illustration  of  what  I  have 
often  seen,  and  have  been  forced  to  perform,  in  the  ventilation 
of  forcing-houses,  and  which  is  more  likely  to  be  exemplified  by 
the  compound  methods  which  I  have  described.  Science  may 
enable  us  to  be  more  watchful  of  atmospheric  phenomena,  and 
may  draw  our  attention  to  facts  which  mere  practice  might  pass 
unnoticed.  But  this  is  a  practical  operation  which  science  has 
not  yet  approached,  and  which,  in  all  her  discoveries,  she  never 
can  approach,  i.  e.,  to  tell  us  the  precise  quantum  of  air  to 
admit  at  different  times  and  under  different  temperatures.  The 
method  of  mixtures  does  not  come  near  it,  and  the  combination 
of  gases  gives  the  gardener  little  scientific  assistance.  We  must 
know  the  nature  and  properties  of  air  at  all  times  and  tempera- 
tures ;  but  the  quantities  and  proportions  in  which  we  are  to 
admit  it  must  be  learned  by  experience  and  strict  observation. 
We  must  watch  its  effects  upon  the  plants,  and  admit  it  in 
7/0-1  ..li  '.-••  • 


282  METHODS    OF    VENTILATION. 

proportions   which   appear,  by   oft-repeated  trials,  to  be  most 
beneficial. 

7.  We  could  describe  several  other  systems  of  ventilation, 
by  what  we  have  called  the  compound  method,  which  have  a 
greater  number  of  wheels  and  rachets,  and  other  kinds  of  ma- 
chinery about  them,  but  which  possess  no  advantage  over  either 
of  the  methods  we  have  described.  One  system,  in  particular, 
has  received  some  countenance,  which  consists  in  opening  by 
the  aid  of  a  spring  instead  of  the  toothed  rod,  as  shown  in  Fig.  56. 
We  have  managed  various  houses  ventilated  by  this  method,  but 
we  must  say  that  it  worked  badly,  although  much  care  had  been 
taken  to  have  the  machinery  properly  fitted  up ;  for  instance, 
where  the  springs  are  of  unequal  strength,  —  and  by  constant 
use  they  very  soon  become  so,  —  you  will  find  a  very  great  irreg- 
ularity in  the  airing  of  the  house,  some  of  them  requiring  to  be 
opened  nearly  full  length,  before  the  others  will  open  a  few 
inches.  Again,  if  some  of  the  sashes  be  stiff  to  open,  those 
that  are  not  so  will  open  freely,  while  the  ones  that  are  hard  to 
move  will  not  open  at  all.  This  has  frequently  caused  us  much 
annoyance.  It  can  never  occur  with  the  toothed  wheel,  as  an 
equal  force  is  exerted  on  each  ventilator  or  sash,  and  every  sash 
is  opened  to  a  regular  distance.  But  if  any  of  the  sashes  be 
stiff  to  open,  then  the  whole  power  applied  is  directed  upon 
them  alone,  until  the  whole  move  together.  The  only  supposed 
advantage  of  the  springs  is,  that  they  do  the  work  silently, 
whereas  a  little  noise  is  made  by  the  rachet-wheels,  —  a  matter, 
in  most  cases,  of  so  trifling  importance,  as  to  be  unworthy  of 
consideration ;  but,  as  drowning  men  catch  at  straws,  so  the  most 
insignificant  circumstance  is  eagerly  seized,  and  magnified  into 
momentous  import,  by  would-be  inventors,  for  the  purpose  of 
palming  off  their  so-called  invention  upon  the  community,  and 
sustaining  its  sinking  reputation.  The  less  machinery  there  is 
about  a  hot-house,  the  better ;  and  that  system  which  does  its 
work  in  the  most  efficient  manner,  with  the  smallest  amount  of 
labor,  and  is  least  likely  to  get  out  of  order,  is  decidedly  to  be 
preferred.  This  is  a  commendation  which  cannot  be  justly 
given  to  some  late  inventions  ;  •  and,  without  wishing  to  throw 


METHODS    OF   VENTILATION.  283 

anything  in  the  way  of  improving  our  present  systems,  or 
discouraging  the  application  of  new  mechanical  inventions  to 
aid  the  practical  operations  of  horticulture,  we  would  say  that 
some  of  these  methods  lately  brought  into  notice  may  be 
justly  compared  to  the  putting  of  extra  wheels  to  a  carriage, 
increasing  the  rattling  and  complexity  of  the  machine,  but  add- 
ing neither  to  the  strength  of  the  structure  nor  the  rapidity  of 
its  course. 

,-, 


SECTION    IV. 

MANAGEMENT      OF      THE      ATMOSPHERE 

1.  NOTWITHSTANDING  all  the  discussion  which  has  taken 
place  upon  the  abstract  question  of  atmospheric  motion,  —  and 
which,  under  certain  temperatures,  as  we  have  already  seen, 
cannot  be  disputed,  —  the  true  principles  of  ventilation  still 
remain  unsettled ;  and  the  mechanical  operation  of  admitting 
the  air  in  larger  or  smaller  quantities  with  facility  does  not, 
in  the  slightest  degree,  remove  the  general  objections  that  have 
been  urged  against  its  effects  on  the  internal  atmosphere.  In 
considering,  therefore,  the  question,  how  far  the  admission  of 
external  air  into  forcing-houses  is  practicable  and  proper,  it  is 
necessary  to  ask,  in  the  first  place,  For  what  purpose  is  the 
admission  of  external  air  resorted  to  under  certain  circum- 
stances ?  and,  secondly,  How  does  it  act  upon  the  atmosphere 
when  admitted  ? 

The  first  of  these  questions  is  of  comparatively  easy  solution  : 
the  latter  requires  more  deep  consideration,  and  more  close 
investigation,  before  we  can  find  a  satisfactory  reply. 

First.  The  necessity  for  ventilation  arises  from  two  prime 
causes,  which  are  briefly  these :  to  regulate  and  reduce  the 
internal  temperature ;  and  to  allow  the  escape  of  impure  air,  or 
that  portion  from  which  some  of  the  essential  constituents  have 
been  abstracted  by  the  plants,  or  in  which  the  natural  equiva- 
lents have  been  changed  in  their  proportions,  and  consequently 
the  health-imbuing  balance  destroyed,  —  an  effect  which  may 
arise  from  various  causes.  The  first  of  these  points  is  a  distinct 
consideration,  forming  an  important  branch  in  vegetable  physi- 
ology: the  others  constitute  a  different  branch  of  scientific 
research ;  but  in  relation  to  our  present  subject,  they  both  merge 
into  one. 


MANAGEMENT    OF    THE    ATMOSPHERE.  285 

The  admission  of  cold  air  as  the  sole  or  principal  agent  in 
regulating  the  internal  temperature  of  a  hot-house  during  win- 
ter, seems  to  be  perfectly  unjustifiable.  There  are,  indeed, 
times  when  it  can  hardly  be  avoided,  during  the  application  of 
artificial  heat ;  but  these  are  exceptions,  rather  than  the  rule. 
Heat,  when  applied  in  early  forcing,  or  to  maintain  the  temper- 
ature of  plant-houses,  is  artificial,  and,  therefore,  so  far  unnatu- 
ral. And  it  appears  still  more  unnatural  to  apply  more  than  is 
necessary,  for  the  purpose  of  admitting  the  external  to  cool 
down  the  internal  atmosphere,  without  having  secured  any 
equivalent  advantage,  but  rather  lost,  by  the  change.  It  is  much 
more  reasonable,  as  well  as  economical,  to  apply  as  much  heat, 
and  no  more  than  is  necessary,  to  raise  the  temperature  to  the 
minimum  point,  or,  at  least,  as  near  this  point  as  is  possible.  It 
may  be  supposed  that  it  would  be  unsafe  to  keep  the  tempera- 
ture so  close  to  the  minimum  point,  lest  the  sudden  external 
changes,  to  which  we  are  subjected  in  this  country  in  winter, 
might  have  an  unfavorable  effect  upon  the  internal  atmosphere ; 
and,  under  certain  circumstances,  this  would  be  the  case, — such 
as  an  imperfect  heating  apparatus,  a  badly  glazed  house,  or  a 
want  of  skill  in  the  management  of  it.  The  necessity  of  main- 
taining the  minimum  rather  than  the  maximum  temperature 
has  been  already  adverted  to  in  the  preceding  chapter;  and, 
instead  of  being  the  exception  to  a  general  rule,  it  is  rapidly 
becoming  the  rule  itself.  We  must  consider  that  the  object  to 
be  kept  in  view  is  to  improve  upon  the  means  at  present  in  use 
to  obtain  these  results,  and  to  obviate  the  risk  and  inconvenience 
which  might  otherwise  ensue  by  their  adoption.  It  will  be 
observed,  that  it  is  not  when  the  mild  and  genial  weather  of 
spring  is  experienced  that  these  remarks  have  any  forcible 
effect,  but  when  the  outward  elements  are  unfavorable  to  the 
development  of  vegetable  life. 

2.  The  atmosphere  of  a  hot-house  is  very  much  influenced 
in  winter  by  the  glazing  of  the  sashes,  and  the  adjustment  of  its 
various  parts.  When  the  laps  of  the  glass  are  open,  there  is  a 
continual  egress  and  ingress  movement  in  the  atmosphere  adja- 
cent to  the  apertures,  extending  generally  over  the  whole  of  its 


286  MANAGEMENT    OF    THE    ATMOSPHERE. 

interior  surface,  but  not  always  affecting  seriously  the  internal 
volume,  except  in  carrying  off  the  rising  particles  of  heated  air, 
the  greater  portion  of  which  is  condensed  by  the  cold  air  imme- 
diately as  it  escapes  from  the  house.  The  consideration  which 
refers  to  the  escape  of  air  in  a  deteriorated  state,  and  the  conse- 
quent necessity  of  admitting  a  fresh  volume  in  its  place,  does 
not  appear  to  offer  any  insurmountable  difficulties  to  the  belief 
that  the  admission  of  fresh  air  in  the  months  of  winter  is  very 
frequently  carried  to  an  injurious  excess.  Although  plants,  in 
the  process  of  their  growth,  and  in  the  discharge  of  their  vital 
functions,  abstract  matters  from  the  atmosphere  around  them, 
there  is  nothing,  even  in  this,  to  render  the  admission  of  cold 
air  in  large  volumes  at  all  necessary.  In  considering  the  nature 
of  the  atmosphere  in  its  relation  to  heat  and  cold,  its  elastic  and 
all-pervading  properties  must  not  be  lost  sight  of.  Under  any 
circumstances,  a  considerable  effect  will  be  produced  by  the 
external  upon  the  internal  atmosphere,  by  radiation  alone ;  and 
with  the  evidence  before  us  of  the  successful  growth  of  plants 
in  situations  so  much  closed  up  as  in  Wardian  cases,  we  cannot 
do  otherwise  than  believe  that  the  interchange  which  takes 
place  between  the  volumes  by  these  causes  is  sufficient  to  secure 
the  health  and  vigor  of  the  plants,  so  far  as  the  admission  of 
air  alone  is  concerned.  If  it  be  argued  that  deterioration  will 
take  place  by  means  of  evaporation  from  flues,  or  pipes,  or  any 
substances  confined  within  the  structure,  or  from  the  decomposi- 
tion of  organic  matter,  the  same  fact  is  presented  of  an  inter- 
change continually  going  on,  and  is  sufficient  to  meet  the  case, 
so  far  as  to  show,  that,  on  this  ground,  at  least,  the  admission 
of  external  air  in  large  volumes  is  not  essential.  Besides,  with 
proper  management,  the  gases  that  are  generated  by  artificial 
heat,  or  by  the  decomposition  of  substances  which  should  find  a 
place  in  .hot-houses,  may  be  combined  with  others  having  an 
affinity  for  them,  and  thereby  not  only  purifying  the  atmosphere 
by  preventing  an  excess  of  particular  agents,  but  also  turning 
those  agents  to  their  legitimate  purpose,  and  rendering  them 
beneficial,  rather  than  detrimental,  to  vegetable  life.  And, 
therefore,  it  can  only  be  in  cases  where  misapplication  or  gross 


MANAGEMENT    OF    THE    ATMOSPHERE.  287 

mismanagement  of  some  kind  or  other  exists,  that  they  can 
possibly  be  productive  of  injury,  or  even  of  inconvenience. 

These  considerations,  then,  would  seem  to  point  out  the  factr 
that  the  admission  of  air  to  any  extent  in  forcing-houses  in  win- 
ter, or  at  a  very  early  period  of  the  season,  cannot  be  said  to  be 
a  matter  of  urgency,  or  necessity ;  neither  can  it  be  grounded  on 
the  plea  that  many  of  our  practical  operations  have  for  their 
foundation,  viz.,  an  expedient  for  a  better,  and  probably  more 
tedious,  method  of  effecting  the  same  results.  Whatever  impro- 
priety may  appear  in  the  above  statement,  it  will  be  fully  justi- 
fied by  its  truth,  —  if  a  dozen  years'  extensive  practice  in  the 
management  of  hot-houses,  both  large  and  small,  and  in  the 
working  of  forcing-houses  throughout  the  winter,  be  worth  any- 
thing, as  well  as  the  evidence  of  many  of  the  best  practical 
gardeners  of  the  present  day.  Then  we  would  say  that  the 
influx  of  large  volumes  of  cold  air  is  decidedly  hurtful,  even  on 
other  grounds  than  those  advanced  in  a  former  part  of  this  chap- 
ter. But,  on  the  other  hand,  the  opposite  extreme  must  also  be 
avoided.  The  process  may  not  be  altogether  dispensed  with, 
although  every  means  ought  to  be  taken  to  modify  its  immedi- 
ate effect  upon  the  internal  atmosphere.  It  does  appear,  never- 
theless, that  the  regulation  of  the  internal  temperature,  i.  e.,  the 
prevention  of  too  powerful  a  degree  of  heat,  when  the  source  of 
that  heat  is  the  sun,  is  the  only  legitimate  end  to  be  effected  by 
the  practice.  If  there  are  any  other  real  advantages,  they  are 
certain  to  follow.  If  air  is  admitted  with  this  only  in  view, — 
and  these  advantages  are  not  likely  to  be  lost  if  air  is  not  admit- 
ted when  not  required  to  effect  this  primary  purpose,  —  periods 
of  bright  sunshine,  then,  may  be  regarded  as  the  only  instances 
in  which  a  recourse  to  the  practice  is  absolutely  necessary. 

3.  From  a  full  investigation  and  consideration  of  this  sub- 
ject, the  conclusion  at  which  we  hare  arrived  is,  that,  with  a 
proper  system  and  routine  of  management,  as  regards  the 
application  of  atmospheric  humidity  and  heat,  the  admission  of 
large  volumes  of  the  external  air  into  the  interior  of  hot-houses 
is  not  by  any  means  so  essential  as  it  is  generally  represented 
to  be.  Whatever  other  differences  of  opinion  may  exist  with 
25 


2SS  MANAGEMENT    OF    THE    ATMOSPHERE. 

respect  to  this  practice,  it  cannot  be  denied  that  a  risk  is  in- 
curred, and  frequently  an  injury  sustained,  when  cold  air  comes 
in  contact  with  the  active  organs  of  tender  plants.  And,  there- 
fore, if  no  other  advantage  be  gained  from  the  practice  than  the 
regulation  of  the  temperature,  then,  except  in  cases  where  the 
heat  is"  increased  by  the  influence  of  the  sun,  and  therefore 
uncontrollable,  it  would  be  a  much  wiser  practice  to  apply  a  less 
amount  of  heat  by  artificial  means,  thus  rendering  it  less  neces- 
sary to  allow  the  superabundant  portion  to  escape,  and  conse- 
quently exposing  the  plants  in  a  less  degree  to  the  risk  to 
which  we  have  alluded. 

4.  Even  in  those  cases  in  which  it  is  really  necessary  to 
have  recourse  to  the  practice  of  admitting  air,  much  injury  will 
be  sustained,  though  it  may  not  be  apparent  at  the  time,  by 
admitting  it  in  a  rash  and  improper  manner.  It  should  be  con- 
trived so  that  the  change  to  be  effected  may  be  brought  about 
gradually,  and  the  cold  and  heated  volumes  should  be  made  to 
intermingle  regularly  together,  and  in  a  way  that  the  internal 
volume  will  be  equally  affected  by  it.  Thus,  if  it  be  desirable 
to  admit  a  quantity  of  air  equivalent  to  the  reduction  of  20° 
of  temperature,  then  the  first  consideration  ought  to  be  the 
external  temperature ;  and  the  apertures  of  admission  ought  to 
be  regulated  according  to  the  calculations  given  at  pp.  164  and 
165,  and  in  such  a  manner  that  the  volume  of  air  within  the 
house  will  not  be  deteriorated  thereby,  nor  deprived  of  those 
gases  which  are  essential  to  vegetable  existence. 

Secondly.  How  does  the  external  air  act  upon  the  internal  at- 
mosphere, when  so  admitted  ?  This  portion  of  our  subject  is  of 
more  difficult  solution,  and  requires  a  closer  investigation,  inas- 
much as  it  is  influenced  by  various  causes,  such  as  the  form  of 
the  structure,  the  method  of  admission,  and  the  material  of 
which  the  interior  part  of  the  house  is  composed ;  for  example, 
a  house  presenting  a  large  surface  of  glass  to  the  morning  sun 
requires  to  be  sooner  ventilated  than  one  whose  largest  glass 
surface  has  a  western  aspect,  and  a  small  quantity  of  air  admit- 
ted early  in  the  morning  will  keep  the  temperature  down  for  a 


MANAGEMENT    OF    THE    ATMOSPHERE. 


289 


longer  period,  than  a  larger  portion,  when  the  temperature  of  the 
house  has  increased  ten  or  twelve  degrees  higher.  Again,  if 
the  top  sashes  be  opened  first,  which  is  generally  done,  then  a 
much  larger  quantity  of  oxygen  and  aqueous  vapor  is  carried 
off  than  at  any  other  period  of  the  day.  We  believe  it  is  the 
practice  of  nineteen  out  of  every  twenty  gardeners,  to  open  the 
top  sashes  first;  then,  when  the  internal  temperature  rises,  and 
more  external  air  is  necessary,  the  top  sashes  are  opened  still 
more ;  and,  last  of  all,  the  front  sashes  are  opened  to  make  a  cir- 
culation;—  a  circulation,  indeed!  By  the  time  the  front  sashes 
are  opened,  the  two  atmospheres  are  generally  equalized.  Now, 
I  would  ask,  how  is  this  circulation  produced,  and  what  are  its 
effects  ?  Not  by  the  superior  density  of  either  atmosphere,  for 
both  are  the  same,  but  by  currents  of  wind,  and  draughts  created 
by  other  causes ;  arid  their  effect  is  to  carry  off  the  moisture 
already  too  much  reduced.  The  annexed  figure  represents  a 

Fi?.  57. 


n  

1  

V"; 

It 

V 

rn 

method  of  admitting  fresh  air  into  a  house  which  obviates  the 
evil  here  complained  of.  The  air  enters  through  the  side-walls 
at  a  a,  then  passes  along  beneath  the  floor,  and  enters  the  house 
in  the  centre  of  the  floor,  at  b.  In  this  instance,  no  air  is 
admitted  at  the  top;  hence,  the  air,  passing  through  these  drains, 
enters  the  house  at  a  higher  temperature  than  if  admitted  at 
the  sides  or  top,  and,  becoming  gradually  warmed  as  it  ascends 
through  the  aperture  in  the  floor,  rises  until  it  is  again  cooled  by 
action  of  the  external  air  upon  the  glass,  then  falls  towards  both 
sides  of  the  house,  producing  a  motion  somewhat  similar  to  that 


290 


MANAGEMENT    OF    THE    ATMOSPHERE. 


shown  by  the  arrows  in  the  foregoing  figure.  By  this  method, 
air  may  be  introduced  into  a  house  at  any  period  of  the  day,  or 
even  at  night;  and  while  every  advantage  arising  from  the 
admission  of  external  air  is  gained,  the  disadvantages  are  done 
away  with,  save  and  except  by  the  crevices  in  the  structure. 
In  winter,  if  cold  air  must  be  introduced  to  regulate  the  internal 
temperature,  some  such  method  as  that  given  above  should  be 
adopted;  but  at  a  more  advanced  season  of  the  year,  when  a 
larger  supply  of  air  is  necessary,  provision  must  be  made  at  the 
sides  for  that  purpose.  As  to  opening  the  top  sashes  first,  and 
keeping  them  open  till  the  last,  it  is  a  practice  for  which  we  are 
unable  to  obtain  any  satisfactory  reason,  and  which  we  think 
will  not  bear  a  strict  investigation.  But,  it  may  be  asked,  how 
is  the  temperature  to  be  reduced,  where,  at  an  advanced  period 
of  spring,  the  sun  shines  more  powerfully,  and  when  the  tem- 
perature of  a  hot-house  will  suddenly  rise  ten  or  fifteen  degrees 
above  the  maximum  point?  To  answer  this  question,  it  is 
necessary  to  consider  whether  there  be  any  other  method  of 
reducing  the  temperature  than  by  expelling  the  heated  air,  by 
the  opening  of  the  top  sashes.  From  what  has  already  been 
said  on  this  point,  we  think  we  are  fully  justified  in  disposing 
of  this  question  in  the  affirmative.  Of  course,  we  do  not  allude 
to  the  ventilation  of  houses  in  summer,  but  in  the  months  of 
autumn,  winter,  and  spring.  By  introducing  the  external  air  in 
the  manner  described  in  the  last  figure,  the  atmosphere  of  a  hot- 
house will  be  reduced  to  any  given  point  as  effectually,  though 
not  so  rapidly,  as  if  the  heated  air  was  expelled  through  the 
sashes  at  the  top  of  the  house.  This  is  accounted  for  by  the 
circumstance  already  explained,  viz.,  that  when  two  columns  of 
air  of  unequal  temperatures  are  mixed  together,  the  tempera- 
ture of  the  whole  is  reduced,  while  its  density  is  increased ;  and 
hence,  so  long  as  the  atmosphere  continues  to  be  heated  by 
reflection  or  radiation,  this  cold  air  will  continue  to  cool  it  down, 
so  that  nothing  is  lost,  while  all  the  essentials  of  vegetation 
contained  in  the  atmosphere  are  retained. 

5.     The  materials  of  which  the  internal  part  of  the  house  is 
composed  have  also  a  powerful  influence  on  the  ventilation  of  a 


MANAGEMENT    OF    THE    ATMOSPHERE. 


291 


hot-house.  Those  houses  whose  internal  bases  are  composed 
of  open  soil  require  less  ventilation  than  those  that  are  paved 
with  stone  or  tiles ;  and  those  that  are  paved  with  tiles,  or  other 
soft  materials,  require  less  than  those  formed  of  hard  and  highly 
reflecting  bodies ;  dark-colored  walls,  also,  are  longer  in  raising 
the  temperature  of  houses  than  walls  painted  white,  and  for  this 
reason  white  is  preferred  to  any  other  color,  as  well  as  for  its 
clean  and  light  appearance  when  contrasted  with  the  dark-green 
foliage  of  the  plants.  But  in  houses  that  are  perfectly  transpa- 
rent on  every  side,  and  admit  abundance  of  light,  there  is  no 
reason  to  suppose  a  dark  color  would  not  be  preferable  to  a  light 
one,  although  we  are  well  aware  that  some  scruples  may  be 
raised  against  it.  Its  propriety,  however,  can  only  be  ques- 
tioned as  a  matter  of  taste,  not  of  utility ;  for,  with  the  advan- 
tages above  alluded  to,  in  a  well-constructed  green-house,  so  far 
as  the  management  of  its  atmosphere  is  concerned,  we  would 
decidedly  prefer  a  house  having  the  interior  painted  with  a  dark 
color,  although  we  are  very  sensible  that  the  effect  produced 
would  be  meagre  and  dull,  and  but  little  calculated  to  harmo- 
nize with  the  floral  inhabitants  of  the  house,  or  the  feelings  of 
those  who  admire  them. 

Fig.  58. 


6.  The  above  cut  represents  a  house  ventilated  by  the  com- 
mon method,  i.  e.,  the  upright  sashes  at  the  sides  and  the  top 
sashes  along  the  roof,  which,  in  span-framed  houses,  are  gener- 
ally about  four  feet  long,  or  nearly  square.  In  summer  this 
method  answers  perfectly ;  but  in  winter  and  early  spring  it  is 


292  MANAGEMENT    O'F    THE    ATMOSPHERE. 

next  to  impossible  to  admit  air  without  injury  to  the  plants,  and 
incurring  the  evils  which  have  been  already  detailed.  Such  a 
house  as  this  should,  by  all  means,  have  these  sashes  made  to 
open,  when  requisite,  but  should  also  be  provided  with  an 
under-ground  method  of  admitting  air,  when  the  weather  is 
unfavorable  for  opening  the  top  arid  side  sashes ;  and,  in  this 
country,  this  may  be  said  to  be  the  case  for  at  least  three 
months  out  of  the  twelve,  during  which  time  air  can  seldom  be 
admitted  in  anything  like  a  sufficient  quantity,  without  a  posi- 
tive, though  perhaps  at  the  time  an  imperceptible,  injury  to 
exotic  plants. 

Various  other  methods  have  been  adopted  for  imparting  to 
the  atmosphere  of  a  hot-house  all  the  freshness  of  the  natural 
atmosphere,  without  a  reduction  of  temperature  corresponding 
to  the  amount  of  cold  air  admitted,  and  also  to  effect  this  with- 
out an  increased  consumption  of  fuel.  The  following  simple 
method  has  been  carried  out  with  pretty  favorable  results :  — 

7.  Suppose  a  house  already  heated  by  the  common  flue. 
We  would  propose  that  a  square  chamber  be  built  over  the  top 
of  the  furnace,  and  embracing  the  neck  of  the  flue  for  two  or 
three  feet,  if  practicable.  This  chamber  should  have  a  drain, 
not  straight,  but  of  a  serpentine  or  zig-zag  form,  laid  through 
it,  one  of  its  ends  communicating  with  the  external  air,  and  the 
other  communicating  with  the  interior  of  the  house.  Into  this 
latter  opening,  a  pipe,  made  of  tin  or  zinc,  should  be  fitted,  of 
sufficient  size  for  the  admission  of  a  good  volume  of  air.  Let 
this  pipe  be  laid  along  the  lateral  surface  of  the  flue  nearest  the 
front  wall  of  the  house,  not  in  immediate  contact  with,  but  sup- 
ported by  bricks,  or  some  other  means,  at  the  distance  of  a  few 
inches  from  the  flue.  Let  that  portion  of  the  tube  which  passes 
along  the  front  be  perforated  with  holes,  to  facilitate  the  escape 
of  the  warm  air,  with  which  it  will  be  filled,  into  the  interior  of 
the  house.  This  done,  let  a  number  of  small  tubes,  —  say  one 
for  each  light,  or  one  for  each  alternate  light, —  be  fixed  through 
the  front  wall,  or  otherwise  as  may  be  convenient,  one  end 
communicating  with  the  external  atmosphere,  and  the  other 
entering  the  perforated  tube.  These  smaller  tubes  should  be 


MANAGEMENT    OF    THE    ATMOSPHERE.  293 

provided  with  valves  to  open  and  shut  at  pleasure,  to  any  extent 
within  the  limits  of  their  diameter,  so  that  the  apertures  of 
ingress  for  the  cold  air  may  be  regulated  by  the  operator  accord- 
ing to  the  state  of  the  weather  and  the  quantity  of  air  required. 
The  size  of  these  tubes  will  Depend  upon  the  size  and  situation 
of  the  house.  For  instance,  if  the  house  contains  a  large  inter- 
nal volume  of  atmosphere,  the  perforated  tube  would  require  to 
be  at  least  eight  inches  in  diameter,  and  the  smaller  about  one 
half  the  size  of  the  large  ones.  And  now  for  its  mode  of  action. 
It  will  be  evident,  that  when  fire  is  applied  to  the  furnace,  its 
cover  (which  forms  the  floor  of  the  chamber)  will  become  heated 
to  a  considerable  degree.  As  soon  as  this  takes  place,  the 
external  valve  of  the  drain,  which  communicates  with  the  main 
tube,  should  be  opened,  when  the  external  air  will  immediately 
rush  in ;  and,  by  having  to  traverse  the  heated  floor  of  the 
chamber  aforesaid,  will  expand  along  the  large  tube  connected  with 
it,  which,  from  being  in  contact  with  the  heated  air,  will  itself 
become  warm.  The  radiation  of  heat,  too,  from  the  surface  of 
the  flue  directly  beneath  it,  will  assist  in  maintaining  the  tem- 
perature of  the  tube  ;  so  that,  although  a  portion  of  the  heated 
air  will  escape  through  the  perforations  in  its  upper  surface, 
enough  will  be  retained  to  effect  the  purpose  intended,  which  is, 
to  neutralize  the  effects  of  the  cold  air  that  will  be  admitted 
through  the  medium  of  the  small  lateral  tubes,  and  which  may 
be  admitted  in  any  quantity,  to  the  full  volume  of  their  admis- 
sion. As  the  warm  air  rushes  along  the  tube,  it  will  mingle 
with  that  admitted  by  the  small  tubes;  and  the  cold  air,  enter- 
ing by  the  latter,  will  thus  be  modified,  while  a  supply  of  fresh 
air  will  at  the  same  time  be  circulated  through  the  atmosphere 
of  the  house. 

8.  The  advocates  of  what  has  been  called  a  "  free  system  of 
ventilation"  have,  like  many  others,  in  practising  and  advocat- 
ing a  favorite  theory,  in  their  excess  of  zeal,  completely  defeated 
the  objects  they  sought  to  secure.  The  sole  object  of  some  of 
the  advocates  of  the  free  system  appears  to  be  the  prevention 
of  a  stagnant  atmosphere.  They  admit  an  unlimited  quantity 
of  atmospheric  air,  at  all  seasons,  to  prevent  this  most  terrible 


294  MANAGEMENT    OF    THE    ATMOSPHERE. 

evil  they  call  stagnation,  and  denounce  the  system  of  sealing  up 
plants  (as  some  of  them  have  termed  it)  from  all  atmospheric 
influence  but  that  exerted  over  them  by  their  own  tainted  arti- 
ficial atmosphere.  Now,  a  stagnant  atmosphere,  or  any  con- 
dition in  the  atmosphere  of  a  hot-house  approaching  to  stagna- 
tion, certainly  cannot  be  otherwise  than  injurious  to  vegetation. 
This  is  a  statement  the  truth  of  which  will  scarcely  be  called  in 
question.  But,  although  the  prevention  or  removal  of  it  has 
always  been  the  chief  object  of  every  scientific  gardener,  it  can- 
not be  said  that  every  gardener,  having  this  aim  in  view,  has 
taken  the  right  way  to  effect  his  purpose  ;  for,  certainly,  what 
is  called  "free"  ventilation  is  very  far  from  being  the  proper 
mode  of  obviating  the  evil ;  and,  in  questioning  the  propriety 
of  the  system  upon  these  grounds,  it  may  be  deemed  necessary 
to  enter  into  an  explanation  of  the  results  attributed  to  this  sys- 
tem of  ventilation,  which  is  said  to  be  requisite  in  order  to 
adapt  an  artificial  air  to  the  circumstances  of  the  plants  growing 
in  it,  and  which  is  supposed  by  some  to  be  in  exact  harmony 
with  the  laws  of  vegetable  physiology,  and  with  all  that  science 
has  unfolded  to  us  respecting  the  effects  of  the  atmosphere  upon 
vegetable  life. 

The  direct  effects  of  ventilation,  of  any  description,  are  two- 
fold, mechanical  and  chemical.  The  former  embraces  the  influ- 
ence which  motion  possesses  over  the  growth  of  plants ;  and  this 
influence  has  never  yet  been  accurately  defined  or  explained  — 
whether  it  be  injurious  or  beneficial,  and  in  what  particular 
degree  it  ceases  to  be  so.  The  latter  comprehends  the  effects  of 
the  various  gases,  and  their  influence  upon  the  vital  functions 
of  vegetable  beings.  To  illustrate  the  effects  of  the  first  of 
these  agents,  viz.,  motion,  we  may  refer  to  the  circumstance 
that  is  well  known,  that  trees  trained  upon  a  wall,  in  ordi- 
nary circumstances,  do  not  grow  to  such  size  as  those  standing 
in  isolated  places ;  but  their  fibre  is  sooner  matured,  and  also 
their  fruit  earlier,  as  well  as  larger  and  more  saccharine.  It  has 
been  asserted  that  wall  trees  do  not  arrive  at  so  great  an  age  as 
others  standing  in  exposed  situations,  —  an  assertion  as  founda- 
tionless  as  it  is  absurd ;  for  it  is  a  well-known  fact,  that  wall  trees 
have  outlived  others  of  the  same  kind,  planted  in  similar  soil, 


MANAGEMENT    OF    THE    ATMOSPHERE.  295 

and  at  the  same  period  with  themselves.  And  yet  this  assertion 
has  been  made  the  basis  of  an  argument  in  favor  of  free  ven- 
tilation. [Experiments  of  Knight,  in  Philosophical  Tramac- 
tions.] 

Surely  a  system  must  be  in  a  tottering  condition  when  such  far- 
fetched arguments  are  resorted  to  for  its  support.  Nor  is  this  a 
solitary  instance  of  irrelevant  arguments  being  brought  to  sup- 
port untenable  systems,  when  in  a  sinking  condition.  When  a 
plant  is  in  a  healthy  and  vigorous  state,  its  sap  is  propelled 
through  its  various  tissues  by  its  own  vital  principle,  aided  by 
the  combined  influence  of  light,  and  heat,  and  moisture.  And 
while  its  vital  principle  remains  unimpaired,  and  these  essentials 
of  its  existence  unexhausted,  its  functions  will  continue  in  a 
state  of  activity,  until  some  cause,  known  or  unknown,  occur  to 
destroy  them. 

Let  us  rehearse  an  argument  which  has  been  advanced  to 
overthrow  the  above  theory.  "  When  a  plant  is  young  and  suc- 
culent, through  all  its  parts,  then  all  goes  on  very  well ;  but 
when  the  plant  becomes  more  matured,  and  its  vessels  less  per- 
vious to  the  flow  of  sap,  from  its  increased  bulk,  its  approach  to 
maturity,  and  probably  its  deadened  susceptibility  to  the  action  of 
light  and  heat,  it  is  evident  that  to  prolong  the  existence  of  such 
a  plant,  a  new  impulse  must  be  communicated  to  its  sap,  by  a 
different  species  of  agency  from  that  which  was  necessary  in  the 
case  of  the  young  plant.  This  impulse  is  imparted  by  motion, 
and  that  motion  is  created  by  the  winds  and  currents  of  the 
atmosphere." 

Such  is  the  sum  and  substance  of  an  argument  which  involves 
the  solution  of  a  most  important  problem  in  vegetable  physiol- 
ogy ;  and,  to  the  merely  superficial  reader,  it  has  something 
very  plausible  in  its  appearance,  but,  unfortunately,  it  will  not 
stand  to  be  strictly  investigated,  for  then  the  very  breezes  that 
are  brought  to  support  it,  would  sweep  it  away.  This  is  more 
especially  true  when  the  illustration  is  applied  to  the  atmos- 
phere of  hot-houses,  upon  which  point  enough  has  been  already 
said  in  this  chapter,  regarding  the  mechanical  effects  of  currents, 
to  render  further  enlargement  on  this  subject  unnecessary. 


SECTION  V. 

CHEMICAL  COMBINATIONS   OF  THE   ATMOSPHERE. 

1.  WITH  respect  to  the  chemical  effects  of  ventilation,  upon 
an  artificial  atmosphere,  there  are  two  important  things  to  be 
kept  in  view,  in  providing  an  artificial  atmosphere  for  plants  in 
a  glazed  structure ;  namely,  the  nourishment  they  ought  to 
receive  from  it,  and  how  to  maintain  it  in  this  nutrient  state. 

It  is  needless,  in  this  place,  to  enter  upon  the  minute  detail 
of  the  various  substances  which  enter  into  the  composition  of 
plants,  or  of  the  various  elements  which  combine  to  form  the 
different  bodies  of  which  they  are  composed,  —  bodies,  in  them- 
selves so  different  in  their  qualities,  yet  so  identical  in  their  for- 
mula, and  consisting  of  the  same  elements,  united  together  in 
the  same  proportions.  This  is  one  of  those  facts  in  chemical 
science  which  appear  so  very  remarkable  to  those  who  have  not 
directed  their  attention  to  chemistry,  but  are  scarcely  capable  of 
being  clearly  comprehended  and  explained,  even  by  those  who 
have  profoundly  studied  this  branch  of  natural  science.  Starch 
and  sugar  —  how  different  their  properties  !  — how  unlike  their 
uses  !  —  how  unequal  their  importance  to  the  human  race  ! 
Yet  they  consist  of  the  same  weights,  of  the  same  substances 
differently  conjoined.  The  skilful  architect  can  put  together 
the  same  proportions  of  the  same  stone  and  cement;  and 
the  painter  can  combine  the  same  colors,  to  produce  a  thou- 
sand varied  impressions  on  the  sense  of  sight.  But  in  the  hand 
of  the  Deity  matter  is  infinitely  more  plastic.  In  his  hands, 
and  at  his  bidding,  the  same  particles  can  unite  in  the  same 
quantities,  so  as  to  produce  the  most  dissimilar  impressions,  and 
on  all  our  senses  at  once. 

A  knowledge  of  the  above  close  relations,  in  composition 
among  a  class  of  substances  occurring  so  abundantly  in  plants, 
imparts  a  degree  of  simplicity  to  our  ideas  of  this  otherwise  so 
very  complicated  subject.  It  does  not  appear  so  mysterious  that 


CHEMICAL   COMBINATIONS.  297 

we  should  have  woody  fibre,  and  starch,  and  gum,  and  sugar, 
occurring  together  in  variable  quantities,  when  we  know  that 
they  all  are  made  up  of  the  same  materials,  in  the  same  pro- 
portions ;  or  that  one  of  these  should  occasionally  disappear 
from  a  plant,  to  be  replaced  in  whole  or  in  part  by  another. 

A  further  question  arises  in  our  minds,  in  connection :  Are 
these  elements  formed  in  an  artificial  atmosphere,  such  as  that 
of  a  hot-house,  from  the  same  combinations  of  matter  as  in 
the  natural  atmosphere  ?  A  reply,  though  probably  not  a  satis- 
factory one,  may  be  drawn  from  the  following  considerations : 

During  the  day  plants  assimilate  carbonic  acid,  and  evolve 
oxygen ;  and  during  the  night  this  system  is  reversed,  although 
we  have  no  accurate  data  from  which  to  conclude  that  the  rela- 
tive proportions  of  these  gases  are,  at  all  times  and  under  all 
circumstances,  the  same.  From  the  latest  experiments,  we  are 
induced  to  suppose  that,  in  an  artificial  atmosphere,  oxygen  is 
the  most  important  element  to  be  attended  to,  in  the  regulation 
of  its  elements;  and  from  the  ^ fact  .that  its  presence,  to  the 
amount  of  21  per  cent,  in  common  atmospheric  air,  is  essential 
to  the  existence  of  animals  and  plants,  there  can  be  little 
doubt  that  it  is  more  frequently  in  deficiency,  than  in  excess, 
in  an  artificial  atmosphere,  and  that  hot-house  plants  are  more 
frequently  injured  by  the  want  of  a  proper  supply,  than  by  an 
excess  of  it  in  the  atmosphere,  when  we  consider  the  quantity 
of  this  substance  which  nature  has  stored  up  for  the  use  of 
plants  and  animals.  Nearly  one  half  of  the  solid  rocks  which 
compose  the  crust  of  our  globe,  —  of  every  solid  substance  we 
see  around  us,  —  of  the  houses  in  which  we  live,  and  of  the 
stones  on  which  we  tread,  —  of  the  soils  which  we  daily  culti- 
vate, —  and  much  more  than  one  half  by  weight  of  the  bodies  of 
all  living  animals  and  plants,  —  consist  of  this  elementary  body, 
oxygen,  known  to  us  only  in  the  state  of  a  gas.  It  may  appear 
surprising  that  any  one  elementary  substance  should  have  been 
formed,  by  the  Creator,  in  such  abundance  as  to  constitute  nearly 
one  half  by  weight  of  the  entire  crust  of  our  globe.  But  this 
is  not  so  surprising,  when  we  consider  that  it  is  on  the  presence 
of  this  element  that  all  animal  and  vegetable  life  depends  !  Nor 
is  it  less  wonderful  that  a  substance,  which  we  know  only  in  a 


298  CHEMICAL   COMBINATIONS 

state  of  thin  air,  should,  by  some  extraordinary  mechanism,  by 
bound  up  and  imprisoned,  in  such  vast  stores,  in  the  solid  moun- 
tains of  the  globe,  —  be  destined  to  pervade  and  refresh  all  na- 
ture, in  the  form  of  water,  and  to  beautify  and  adorn  the  earth 
in  the  solid  parts  of  animals  and  plants.  But  all  nature  is  full 
of  similar  wonders,  and  every  step  we  advance  in  the  study  of 
the  principles  of  our  art,  we  cannot  fail  to  perceive  the  united 
skill  and  bounty  of  the  same  great  Contriver. 

2.  It  has  been  stated  by  some  philosophers,  that  when  the 
leaves  of  plants  are  in  a  state  of  rest,  their  respiration  is  reduced 
to  its  minimum  point,  and  that  it  increases  within  certain  limits, 
as  motion  is  communicated  to  them  by  the  action  of  a  current 
of  air.  Now  this  may  be  perfectly  correct,  and  very  likely  is 
so ;  although,  under  natural  conditions,  the  suspension  of  respi- 
ration has  never  been  accurately  ascertained.  Various  physiol- 
ogists have  attempted  to  discover  the  minimum  of  respiratory 
suspension,  under  certain  atmospheric  conditions,  but  without 
any  satisfactory  results.  But  it  does  not  require  the  discovery 
of  this  delicate  point,  to  decide  on  the  propriety  or  utility  o£ 
atmospheric  motion.  That  a  certain  motion  in  the  atmosphere 
is  beneficial,  we  know;  but  then,  it  becomes  a  question  of  degree. 
We  know  that  the  gentle  zephyr  is  favorable  to  vegetation,  and, 
even  in  a  hot-house,  we  have  some  reason  to  suppose  it  is  so, 
under  certain  circumstances,  and  to  a  certain  extent.  Now  it  is 
under  the  uncertain  circumstances,  and  the  uncertain  extent  to 
which  this  practice  is  carried,  that  we  have  any  objections  ;  for 
such  circumstances,  and  such  indiscriminate  abuse  of  the  prac- 
tice, we  know  to  exist ;  and  hence  the  chemical  effects  of  venti- 
lation, in  the  majority  of  cases,  instead  of  promoting  respiration, 
rather  tend  to  prevent  it,  by  depriving  the  atmosphere  of  the 
principal  element  that  nature  has  designed  to  carry  on  the  work. 

The  mechanical  and  chemical  influences  are  intimately  con- 
nected with  each  other,  so  that  to  secure  the  chemical  ad- 
vantage of  ventilation,  I  presume  consists  in  maintaining  the 
proper  equivalents  of  the  atmosphere,  which  nature  has  deter- 
mined as  essential  to  the  development  of  vegetation.  If  this 
view  be  correct,  the  grand  and  important  practical  question 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  299 

suggests  itself,  whether,  in  the  atmosphere  of  hot-houses  gener- 
ally, these  essentials  to  the  growth  of  plants  be  suitably  provided. 
By  chemical  research,  we  find  that  nitrogen  forms  only  a 
small  portion  of  plants,  but  it  is  never  entirely  absent  from  any 
part  of  them  ;  even  when  it  is  not  found  in  any  particular  organ,, 
it  is  found  to  be  present  in  the  fluids  that  pervade  it.  Many 
experiments  have  been  instituted,  with  the  view  of  ascertaining 
expressly,  by  what  particular  organs  nitrogen  entered  into  the 
plant,  and  in  what  form  it  enters.  Indeed,  this  is  a  question 
which  at  present  occupies  much  attention.  It  is  well  known 
that  the  leaves  of  plants  absorb  gaseous  elements  largely  from 
the  atmosphere,  both  free  and  in  a  combined  state,  and  we  might, 
therefore,  expect  that  some  of  the  nitrogen  of  the  air  would,  by 
this  channel,  be  admitted  into  their  circulation.  This  view, 
however,  is  not  confirmed  by  any  of  the  experiments  heretofore 
made,  with  the  view  of  investigating  the  action  and  functions  of 
the  leaves.  We  are  not  at  liberty  to  assume,  therefore,  that 
any  of  the  nitrogen  which  plants  contain,  has  in  this  way  been 
derived  directly  from  the  atmosphere.  It  may  be  the  case,  but 
it  is  not  yet  proved.  There  is  little  doubt,  however,  that  nitro- 
gen enters  the  roots  of  plants,  in  a  state  of  solution ;  but  the 
quantity  they  thus  absorb  is  uncertain ;  it  is  supposed  to  be 
small,  and  must  be  variable.  Therefore,  by  whatever  organs  it 
finds  an  entrance  into  plants,  and  in  whatever  quantity  it  may 
be  present,  the  question  still  remains,  that  it  is  the  ammonia  of 
the  atmosphere  that  chiefly  furnishes  nitrogen  to  plants. 

3.  In  a  former  part  of  this  treatise,  while  treating  on  the 
subject  of  heating,  by  means  of  fermenting  manure,  we  have 
alluded  to  the  extraordinary  effects  of  ammonia  upon  plants.  It 
is  unnecessary,  at  present,  to  recapitulate  what  has  already  been 
said  on  that  interesting  point.  It  has,  we  think,  been  clearly 
established,  that  the  difference  between  a  hot-bed  of  manure,  and 
that  heated  by  any  other  means,  does  not  lie  in  the  quality  of 
the  heat  generated ;  as  we  know  full  well  that  a  hot-bed  of 
manure,  warmed  beyond  a  certain  point,  will  burn  the  roots 
of  plants  as  quickly  as  one  heated  by  any  other  method  to  the 
same  temperature ;  nor  does  it  consist  in  any  life-giving  proper- 


300  CHEMICAL    COMBINATIONS 

ties,  possessed  exclusively  by  stable  manure,  for  we  know,  also, 
that  by  placing  living  plants  in  a  hot-bed,  newly  made,  even  if 
the  heat  of  the  bed  be  kept  from  injuring  the  roots,  they  will 
soon  cease  to  exist  as  living  beings,  purely  from  an  excess  of 
those  very  gases  which,  in  proper  proportions,  add  so  much  to 
their  natural  luxuriance.  Plants  are  more  sensitive,  and  more 
easily  affected,  with  regard  to  life  and  health,  than  many  living 
animals.  Many  persons,  who  have  paid  little  attention  to  veg- 
etable physiology,  may  be  dubious  of  this  fact,  but  it  is,  neverthe- 
less, true.  The  atmosphere  of  a  hot-house  may  be  impregnated 
with  ammoniacal  and  other  gases,  beneficial  to  vegetable  life, 
without  being  offensive  to  the  ordinary  visitor,  or  even  detected 
by  him  in  the  atmosphere  of  the  house.  Besides,  it  is  so  quick- 
ly absorbed  by  the  plants,  that  it  has  to  be  saturated  almost  to 
excess  before  much  smell  is  sensibly  felt.  We  have  carried  on 
the  practice  daily,  of  impregnating  the  atmosphere  of  a  green- 
house with  carbonate  of  ammonia,  by  dissolving  it  in  water  and 
sprinkling  through  the  house,  without  the  ammonia  being  de- 
tected, except  by  the  acute  olfactory  organs  of  the  experienced 
chemist,  except,  perhaps,  when  the  atmosphere  was  impregnated 
to  an  excess,  which,  by  way  of  experiment,  was  sometimeF  the 
case. 

4.  This  subject  now  resolves  itself  into  the  following  consid- 
erations :  — 

(1.)  Which  gases  is  it  necessary  to  generate  artificially,  for 
the  purpose  of  increasing  the  capacity  of  the  atmosphere  of  a 
hot-house  to  sustain  vegetable  life  in  a  state  of  vigor  and  health- 
fulness  ? 

(2.)  How  are  we  to  determine  the  precise  proportions  of  each, 
so  that  we  may  keep  as  near  as  possible  to  that  point  of  health- 
fulness,  which  lies  midway  between  deficiency  and  excess  ? 

In  replying  to  the  first  question,  it  is  not  necessary  to  enter 
into  an  elaborate  detail  of  the  various  volatile  gases  which 
arise  from  the  combination  of  the  prime  elements  of  the  organic 
world,  in  different  proportions,  and  which  are  absorbed  by  plants. 
It  may  be  sufficient  for  my  present  purpose,  to  notice  that  grand 
stimulus  of  vegetation  already  alluded  to,  viz.,  ammonia,  which, 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  301 

as  we  have  already  seen,  plays  such  an  important  part  in  the 
progress  of  vegetable  life.  This  gas,  though  composed  of 
hydrogen  and  nitrogen,  is  very  unlike  these,  or,  indeed,  any 
other  gases  with  which  the  chemist  is  yet  acquainted.  It  is 
possessed  of  a  most  powerful  penetrating  smell,  which  is  familiar 
to  almost  every  one  as  hartshorn  and  smelling-salts.  In  excess, 
it  suffocates  living  animals,  though  it  requires  a  very  considera- 
ble preponderance  in  the  atmospheric  volume  to  destroy  either 
animal  or  vegetable  life.  Illustrations  of  this  fact  we  have  fre- 
quently observed  in  fumigating  a  pit,  or  house,  for  the  destruc- 
tion of  aphides,  and  other  insects ;  but  it  destroys  both,  much 
more  rapidly,  when  evolved  at  a  high  temperature,  as  we  fre- 
quently find  it  in  hot-beds  of  dung,  when  plants  have  been 
placed  in  them  before  the  gas  and  heat  had  somewhat  subsided, 
as  well  as  in  vineries,  which  we  have  seen  filled  with  ammoni- 
acal  gas,  when  the  atmosphere  was  near  100  degrees,  when  the 
edges  of  the  tender  leaves  appeared  as  if  they  had  been  nipped 
with  frost,  but  the  insects  were  not  entirely  destroyed.  In 
fumigating  frames  and  pits  with  this  and  other  gases,  we  have 
seen  some  kinds  of  tender-leaved  plants  completely  destroyed, 
while  many  of  the  insects,  tenacious  of  life,  were  uninjured, 
which  has  fully  satisfied  me  of  the  truth  of  the  statement  already 
made,  i.  e.,  that  the.  generality  of  tender  plants  are  more  sensi- 
tive of  noxious  gases  than  living  animals,  although  few  may  be 
inclined  to  believe  it,  and  their  disbelief  is  too  often  manifested 
in  the  treatment  their  plants  receive.  There  can  be  little  doubt 
that  it  is  this  gas,  in  a  certain  proportion  of  atmospheric  air, 
that  produces  the  luxuriance  of  plants,  when  combined  with  the 
mild  heat  of  a  dung-bed.  Were  we  to  ask  a  chemist,  What  are 
the  manures  which,  in  a  fluid  or  gaseous  state,  can  in  these 
forms  be  presented  to  the  atmosphere,  and  diffused  among  living 
plants,  in  a  hot-house  ?  —  he  would  answer,  "  Ammonia,  obtain 
it  from  whatever  source  you  may,  either  in  a  simple  or  combined 
state  ;"  and  as  hitherto  our  chief  supply  of  this  substance,  which 
we  have  had  to  deal  with  in  the  common  operations  of  garden- 
ing, has  been  found  in  our  hot-beds  of  stable  manure,  resulting 
from  the  decomposition  of  vegetable  matter,  principally  the  nitro- 
geneous  substances  contained  in  corn  and  other  matter  on  which 


302 


CHEMICAL   COMBINATIONS 


the  horses  have  been  fed,  with  the  compounds  of  salts  and  ani- 
mal matter,  all  of  which  contain  within  themselves  a  tendency 
to  rapid  putrefaction,  and  necessarily  evolve  a  large  amount  of 
ammonia.  This  is  the  principal  source  which  gardeners  have 
had  to  draw  upon  for  a  supply  of  this  agent ;  and,  although 
exercising  the  most  striking  effects,  it  is  rather  remarkable  that 
the  cause  of  these  effects  should,  until  lately,  remain  a  mystery 
to  gardeners  in  general,  and  that  the  same  elements,  in  a  more 
concentrated  state,  should  not,  in  other  circumstances,  be  applied 
to  produce  the  same  results. 

The  second  question  is,  perhaps,  of  more  difficult  solution. 
Plants  are  living,  organized,  beings,  and  acted  upon,  atmospher- 
ically, chiefly  by  the  glands  that  cover  the  surface  of  the  leaves ; 
and  abundant  evidence  exists,  that  they  are  as  susceptible  of 
either  injury  or  benefit,  through  the  medium  of  the  atmosphere 
to  which  they  are  exposed,  as  animal  life,  and  our  ignorance  of 
the  effect  of  houses  artificially  heated,  upon  the  delicate  organ- 
ism of  plants,  is  only  accounted  for  from  the  fact,  that  com- 
paratively little  attention  has  yet  been  paid  to  this  branch  of 
horticultural  science  by  practical  gardeners,  and  still  less  has  it 
been  applied  to  the  culture  of  exotic  plants.  If,  for  instance, 
we  take  a  plant  from  the  open  ground,  where  it  is  fully  exposed 
to  the  pure  air,  plant  it  in  a  pot,  and  place  it  in  a  close  living 
room,  or  in  a  hot-house,  the  effect  will  be  rendered  obvious  by 
the  altered  appearance  of  the  plant.  Again,  if  we  take  a  plant 
newly  potted,  and  otherwise  disturbed  in  the  roots,  and  set  it  in 
an  arid  situation,  and  fully  exposed  to  the  air,  the  leaves  will 
be  withered  and  dried  up  in  a  few  hours,  and  probably  the  death 
of  the  plant  will  be  the  issue.  But  if  the  plants  are  placed  in 
a  close,  moist  atmosphere,  the  results  will  be  very  different. 
Now  these  illustrations  are  common,  and,  in  themselves,  exceed- 
ingly simple,  so  much  so,  that  we  frequently  observe  them,  and, 
if  asked  the  cause,  we  give  a  kind  of  generalizing  reply,  by 
attributing  it  to  the  sun,  or  some  such  cause,  which  is  well 
known  to  be  the  principal  origin  of  heat,  yet  they  serve  to  show 
how  susceptible  plants  are  of  influences  which,  strictly  speak- 
ing, are  neither  dependent  upon  heat  nor  cold,  although  these 
two  latter  elements  are  almost  the  only  ones  which  we  are  in 


OF   THE    ATMOSPHERE    OF    HOT-HOUSES.  303 

the  habit  of  supplying  to  our  plants  by  measure,  and  that,  too, 
in  the  most  unnatural  proportions,  while  the  ammoniacal  and 
hygrometrical  condition  of  the  atmosphere  is  generally  left  to 
uncontrolled  transmutations  of  chance. 

5.  It  may  be  asked,  "  What  guide  have  we  to  ascertain  the 
condition  of  the  atmospheric  gases  ?  " 

In  the  present  state  of  our  knowledge  of  gaseous  bodies,  their 
presence  or  preponderance  in  the  atmosphere  of  hot-houses  must 
be  little  else  than  a  matter  of  conjecture.  An  experienced  gar- 
dener, on  entering  his  hot-house  in  the  dark,  can  tell  pretty 
accurately  what  degree  of  temperature  the  atmosphere  of  the 
house  is  standing  at,  by  the  sensation  produced  upon  his  face, 
or  by  the  wave  of  his  hand  in  the  air.  Now,  in  regard  to  the 
excess  of  volatile  gases  floating  in  the  atmosphere,  the  organs  of 
smell  are  much  more  delicate  indicators  than  the  sense  of  feeling. 
This  is  more  especially  the  case  when  the  house  is  close,  and  the 
temperature  pretty  high;  for  then  the  ammonia,  being  little  more 
than  half  the  weight  of  the  common  atmosphere,  [more  nearly 
three  fifths,  its  specific  gravity  being  0.59,  that  of  air  being  1 J 
hence,  when  liberated  on  the  floor,  or  on  the  flue,  pipes,  tank,  or 
other  heating  apparatus,  it  readily  rises  and  mingles  with  the 
atmosphere ;  and  although  it  requires  a  considerable  proportion 
of  it  in  the  atmosphere  to  be  injurious,  or  even  offensive  to  the 
senses,  it  is,  nevertheless,  easily  detected  by  those  acquainted 
with  this  gas,  even  when  present  in  small  quantities,  and  the 
experienced  organs  of  the  practical  man  have  no  difficulty  in 
deciding  whether  or  not  it  is  present  in  excess.  On  entering  a 
hot-house,  when  oxygen  arid  aqueous  vapor  are  deficient  in  the 
atmosphere,  this  fact  is  at  once  detected  by  the  oppressive  burnt 
smell  which  pervades  the  house.  Saturate  the  atmosphere  with 
water,  oxygen  is  generated,  and  the  smell  ceases.  The  carbonic 
acid,  which  previously  existed  in  excess,  combines  with  the  oxy- 
gen, and  is  transformed  into  carbonic  acid  gas,  in  which  state  it 
is  assimilated  by  the  plants.  In  the  state  of  vapor,  water  exer- 
cises a  wonderful  influence  over  the  atmosphere  of  a  hot-house, 
and  ministers  most  materially  to  the  life  and  growth  of  plants. 
It  is  in  the  form  of  water,  indeed,  that  nature  introduces  the 
26* 


304  CHEMICAL   COMBINATIONS 

greater  portion  of  the  oxygen  which  performs  so  important  a 
part  in  the  numerous  and  diversified  changes  which  are  contin- 
ually taking  place  in  the  interior  of  plants.  Few  changes  are 
really  more  wonderful,  in  chemical  physiology,  than  the  vast 
variety  of  transmutations  which  are  constantly  going  on  through 
the  agency  of  the  elements  of  water. 

It  rarely,  perhaps  never,  happens  that  we  find  the  same 
unhealthy  and  disagreeable  smell  in  the  external  atmosphere, 
which  we  frequently  perceive  in  forcing-houses  after  a  strong 
fire  has  been  kept  up  during  the  night.  Sometimes  this  condi- 
tion may  occur  in  the  confined  streets  of  closely-built  cities,  and 
in  the  vicinity  of  chemical  works,  where  the  heavier  gases  rise 
into  the  air  in  a  rarefied  state,  and,  on  cooling,  fall  again  to  the 
surface  of  the  earth,  producing  sometimes  injurious  conse- 
quences. The  combustion  of  fuel  for  the  production  of  artificial 
heat  produces  also  carbonic  acid  gas  in  great  abundance.  And 
to  form  this  gas  the  oxygen  is  drawn  from  the  plants  to  form 
the  combination ;  and  in  this  way  the  deficiency  of  oxygen,  so 
much  felt  in  forcing-houses,  may  partly  be  accounted  for.  Oxy- 
gen must  exist  ia  the  atmosphere  to  the  amount  of  21  per  cent, 
of  its  bulk  to  be  capable  of  supporting  animal  and  vegetable  life 
in  a  state  of  vigorous  development ;  and  when  this  proportion  is 
reduced,  the  plants  under  its  influence  must  suffer  accordingly. 
The  most  convenient  method  of  supplying  the  atmosphere  with 
oxygen  is  by  saturation  with  water,  which  latter  element  con- 
tains a  very  large  amount  of  this  gas,  —  every  nine  pounds  of  this 
liquid  containing  no  less  than  eight  pounds  of  oxygen.  In  the 
interior  of  plants,  water  undergoes  continual  decomposition  and 
recomposition.  In  its  fluid  state  it  finds  its  way  and  exists  in 
every  vessel  and  in  every  tissue;  and  so  slight,  it  would  appear, 
in  such  situations,  is  the  hold  which  its  component  elements 
have  upon  each  other,  or  so  strong  their  tendency  to  combine 
with  other  substances,  that  they  are  ready  to  separate  from  each 
other  at  every  impulse,  yielding  now  oxygen  to  one,  now  hydro- 
gen to  another,  as  the  production  of  the  several  compounds 
which  each  organ  is  destined  to  elaborate  respectively  demands. 
Yet  with  the  same  readiness  do  they  re-attach  themselves,  and 
cling  together,  when  new  metamorphoses  require  it. 

6.     In  the  constitution  of  the  natural  atmosphere  we  are  at 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  305 

no  loss  to  discover  its  beautiful  adaptation  to  the  wants  and 
structural  development  of  animal  and  vegetable  life.  The  excit- 
ing effect  of  pure  oxygen  on  the  animal  economy  is  diluted  by 
the  large  admixture  with  nitrogen;  the  quantity  of  carbonic 
acid  present  is  sufficient  to  supply  food  to  the  plant,  while  it  is 
not  so  great  as  to  prove  injurious  to  the  animal;  and  the  watery 
vapor  suffices  to  maintain  the  flexibility  of  the  parts  of  both 
orders  of  beings,  without  being  in  such  a  proportion  as  to  prove 
hurtful  to  either.^ 

The  air,  thus  charged  with  these  gases,  by  its  subtilty  diffuses 
itself  everywhere.  Into  every  pore  of  the  soil  it  make  its  way. 
When  there,  it  yields  its  oxygen,  or  its  carbonic  acid,  to  the 
dead  vegetable  matter  existing  therein,  or  to  the  living  roots. 
When  the  soil  is  heated  by  the  sun,  the  gases  that  are  impris- 
oned therein  expand  arid  partially  escape,  and  are  as  before 
replaced  by  other  particles  of  air  when  the  heat  of  the  sun  is 
withdrawn. 

By  the  action  of  these  and  other  causes,  a  constant  circulation 
is  kept  up,  to  a  certain  extent,  between  the  atmosphere  on  the 
surface,  which  plays  among  the  leaves  and  stems  of  plants,  and 
the  air  which  mingles  with  the  soil  and  ministers  to  the  roots; 

*  The  mutual  influence  of  animal  and  vegetable  life  is  well  illustrated 
by  the  following  experiment.  Into  a  glass  vessel,  filled  with  water,  put 
a  sprig  of  a  plant  and  a  fish.  Let  the  vessel  be  tightly  corked,  and 
placed  in  the  sun.  The  plant,  under  the  influence  of  solar  light,  will 
soon  commence  the  process  of  liberating  oxygen.  This  being  absorbed 
by  the  water  is  respired  by  the  fish,  which,  in  its  turn,  gives  out  car- 
bonic acid  to  be  decomposed  by  the  plant.  Remove  the  vessel  from  the 
sun-light ;  the  plant  will  cease  to  give  out  oxygen,  and  the  fish  will 
soon  languish,  and  revive  when  placed  in  the  light.  The  moving  power 
of  this  beautiful  system  is  the  solar  light.  The  balance  is  thus  pre- 
served ;  and  the  atmosphere,  even  if  of  limited  extent,  cannot  be  sensibly 
changed  through  all  time. 

It  is  not  intended  to  intimate  that  it  is  in  the  removal  of  carbonic  acid 
from  the  atmosphere  that  plants  are  most  essential  to  animals,  —  the 
supply  of  organic  matter  ready  for  assimilation  is  of  more  immediate 
importance  than  this,  —  but  to  show  that  their  influence  is  mutually 
conservative,  preventing  that  change  in  the  constituents  of  the  atmos- 
phere which  would  eventually  be  fatal  to  organic  life. —  [Wyman  on 
Ventilation.} 


306  CHEMICAL   COMBINATIONS 

and  will  also  suffice  to  show  the  absolute  necessity  of  maintain- 
ing an  adequate  supply  of  aqueous  vapor  in  the  atmosphere  of 
our  hot-houses,  as  well  as  the  imperative  necessity  of  studying 
and  making  ourselves  acquainted  with  the  nature  and  qualities 
of  the  atmospheric  elements.  Science  has  already  done  much, 
and  is  still  doing  more,  for  the  art  of  horticulture.  We  have 
the  thermometer,  by  which  we  can  deal  out  heat  and  cold  by 
the  measure.  We  have  the  barometer,  by  which  we  can  ascer- 
tain to  a  decimal  the  weight  or  density  of  the  air.  We  have, 
also,  the  hygrometer,  by  which  we  can  tell  the  precise  amount 
of  its  contained  moisture,  —  although  this  latter  instrument  is 
but  little  used  in  practical  horticulture,  —  and  we  hope  the  time 
is  not  distant  when  it  will  find  a  place  side  by  side  with  the 
thermometer  in  our  hot-houses,  to  which  it  does  not  yield  one 
iota  of  importance,  of  interest,  or  of  utility.  When  shall  we  have 
an  instrument,  equally  simple  and  efficient  as  these,  with  which 
we  may  ascertain  the  proportions  of  its  gaseous  elements,  so 
that  we  can  regulate  the  constituents  of  an  atmospheric  volume 
as  easily  as  we  can  do  its  heat  and  moisture  ?  Such  an  instru- 
ment is  much  wanted  by  exotic  horticulturists,  and  we  trust 
something  of  the  kind  will  be  yet  brought  into  use.  Such  an 
instrument  could  be  applied  to  excellent  purpose,  and  would  be 
an  incalculable  boon  conferred  on  gardening,  —  one  almost  un- 
equalled in  importance  at  the  present  day,  and  would  be  of 
immense  utility  in  all  the  higher  and  more  difficult  branches 
of  exotic  horticulture. 

7.  There  is,  probably,  no  individual  branch  of  natural  science 
so  useful  in  itself  to  the  practical  gardener  as  a  knowledge  of 
the  various  atmospheric  phenomena  which  occur  in  hot-houses, 
as  well  as  out  of  doors ;  and  without  we  study  the  one,  we  can 
have  but  little  knowledge  of  the  agencies  which  regulate  the 
other.  That  a  practical  foreknowledge  or  intuitive  perception 
of  the  ordinary  changes  of  the  atmosphere  is  an  acquirement 
which  may  certainly  be  obtained,  to  a  very  considerable  extent, 
without  the  aid  of  science,  is  beyond  a  doubt.  We  find  that  the 
untutored  savage,  taught  only  by  his  own  observation,  or  instinct- 
ively, is  regulated  in  his  movements  by  an  unerring  perception 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  307 

of  the  coming  changes  of  his  own  peculiar  climate,  and  many 
of  the  lower  animals  are  also  highly  sensitive  of  changes  ap- 
proaching, especially  the  feathered  tribes.  Every  person  is 
more  or  less  familiar  with  these  facts.  We  reason,  therefore, 
from  the  lesser  to  the  greater;  and  if,  in  the  absence  of  compara- 
tive calculation,  or  the  comparison  of  the  results  of  one  season 
with  another,  —  if,  in  fact,  we  consider  what  are  the  attainments 
of  instinctive  knowledge  alone,  we  are  justified  in  believing 
that,  from  established  principles,  the  result  of  learned  inquiry 
and  deep  investigation,  and  the  application  of  science  extending 
over  many  successive  years,  many  useful  facts  are  already 
known  and  clearly  explained  for  our  practical  guidance.  Aided 
by  these  researches,  man's  ingenuity  has  already  turned  these 
elements  to  a  useful  account,  and  made  them  subserve  his  pur- 
pose, powerful  though  they  be.  But,  in  rendering  these  pow- 
erful and  all-pervading  elements  subservient  to  our  will,  the 
object  of  that  will  must  be  undeviatingly  directed  to  the  imita- 
tion of  nature.  To  exceed,  or  even  reach,  in  every  case,  the 
perfection  of  the  pattern,  is  impossible ;  but  the  more  closely  it 
is  kept  in  view,  and  the  more  nearly  it  is  attained  in  our  artifi- 
cial performances,  the  more  perfect  will  that  performance  be, 
and  the  more  exactly  will  our  own  ends  be  answered.  Any 
departures  from  the  principles  suggested  by  the  examples  set 
before  us  in  nature,  through  an  over-hasty  desire  to  arrive  at 
the  object  by  a  nearer  road,  not  only  defeats  the  intended  pur- 
pose, but  also  makes  the  ultimate  attainment  of  that  object 
much  more  troublesome  and  expensive.  The  subject  of  this 
treatise  affords  too  many  examples  of  this  fact;  and,  though 
these  examples  may  remain  unnoticed  by  some,  and  uncared 
for  by  others,  their  baneful  influence  on  the  progressing  art 
of  horticulture  is  neither  distant  nor  obscure.  The  various 
structures  for  cultivation  are,  indeed,  much  improved  of  late 
years ;  so,  also,  are  the  methods  of  applying  heat,  air,  vapor, 
and  water.  All  are  so  easy,  and  so  much  improved,  that  we 
sometimes  hear  practical  men  observe,  that  this  or  that  principle 
or  system  cannot  be  beaten  or  improved ;  yet  the  very  best  con- 
structed apparatus,  and  the  most  perfect  methods  of  applying 
heat,  vapor,  air,  and  light,  are  capable  of  astonishing  improve- 


308  COMBINATIONS    OF    THE    ATMOSPHERE. 

ments.  And  no  doubt  the  next  twenty  years  will  bring  many 
a  hidden  treasure  to  light,  and,  in  that  time,  even  our  most 
approved  systems  of  applying  heat,  etc.,  will  be  altogether 
economized  and  reformed. 


SECTION    VI. 

PROTECTION      OF      PLANT-HOUSES       DURING      COLD 
NIGHTS. 

1.  BEFORE  concluding  this  brief  treatise  on  horticultural 
buildings,  we  will  just  cursorily  advert  to  one  more  topic  con- 
nected therewith,  which  we  are  inclined  to  think  is  of  far  more 
importance  than  is  generally  credited,  at  least,  it  certainly  is  so, 
if  we  are  to  judge  from  the  degree  of  its  practical  application, 
viz.,  the  protection  of  plant-houses,  and,  more  especially,  forcing- 
houses,  during  cold  nights,  both  with  a  view  to  the  economizing 
of  fuel,  and  the  equalization  of  heat.  If  duly  considered,  the 
advantages  of  such  covering  are  obvious.  The  low  degree  of 
night  temperature,  which  the  best  cultivators  of  the  present  day 
agree  in  regarding  as  being  most  favorable  to  the  healthfulness 
and  general  welfare  of  their  plants,  would  depend  upon  the  com- 
bustion of  fuel,  so  much  less,  in  proportion,  as  the  escape  of 
the  internal  heat,  by  radiation  and  otherwise,  was  prevented  by 
means  of  a  covering  exterior  to  the  conducting  surface  of  the 
glass. 

The  manifest  advantage  of  such  a  protecting  body  does  not 
wholly  consist,  in  the  economizing  of  fuel.  In  such  a  variable 
climate  as  we  have  in  the  New  England  States,  with  the  exter- 
nal atmosphere  acting  on  the  glass  at  a  temperature  of  25  or  30 
degrees  below  the  freezing  point,  it  is,  then,  almost  under  any 
system  of  heating,  unavoidably  necessary  to  apply  an  excess  of 
artificial  heat,  to  ensure  the  safety  of  the  plants  against  injuri- 
ous depressions  of  temperature.  Now,  if  a  covering  of  non- 
conducting materials  be  employed  to  intercept  the  action  of  the 
changing  atmosphere  upon  the  surface  of  the  glass,  the  plants 
will  be  as  safe  at  a  much  lower  internal  temperature,  as  if  no 
such  protection  were  afforded  them,  with  a  high  temperature. 
The  plants,  therefore,  will,  under  these  circumstances,  be  in  a 


310          PROTECTION  OF  PLANT-HOUSES  DURING  COLD  NIGHTS. 

condition  more  conducive  to  their  health,  than  if  their  safety  from 
excess  of  cold  had  involved  their  submission  to  a  higher  degree 
of  artificial  heat  during  the  night. 

Night  coverings,  moreover,  seem  to  afford  facilities  for  night 
ventilation, — a  time  when  ventilation,  of  all  others,  appears  to  be 
most  necessary;  for  then,  deleterious  gases  are  generated  in 
the  greatest  abundance,  and  the  agitation  and  circulation  of 
the  atmosphere  is  most  required.  We  have  seen  that  motion 
and  interchange  of  atmospheric  particles  are,  to  a  certain  extent, 
beneficial  to  the  health  of  plants  ;  and  as  their  functions  are  in  a 
state  of  activity  during  the  night,  motion  and  circulation  are  as 
necessary  during  that  time  as  at  midday.  If  a  close  confined 
atmosphere  be  injurious  to  plants  in  the  daytime,  it  must  be 
more  so  during  the  night,  especially  when  artificial  heat  is  in 
process  of  generation.  This  fact  is  now  beginning  to  be  recog- 
nized by  the  sounds,  which  are  echoing  in  our  ears  —  though  as 
yet  but  faintly,  —  the  injunction,  to  keep  a  little  air  on  all  night; 
and  which  is  responded  to  by  the  practice  of  the  best  cultivators 
of  the  present  day. 

Under  ordinary  circumstances,  where  artificial  heat  is  neces- 
sary, there  is  some  risk  in  following  these  recommendations. 
A  chilly  blast,  which  cannot  be  refused  admission  when  the  bar- 
rier to  ingress  is  removed,  would  deal  death  and  desolation 
around ;  and  if  this  would  be  liable  to  happen  in  the  daytime, 
when  attendants  are  at  hand,  the  risk  would  be  still  greater  at 
night,  when  none  were  present  to  guard*igainst  it ;  and,  under 
the  most  favorable  circumstances,  night  ventilation,  if  carried  to 
any  extent,  would  involve  a  great  loss  of  heat.  It  becomes, 
therefore,  a  question,  if  the  motion  and  circulation  of  the  inter- 
nal atmosphere  during  the  night  could  not  be  so  far  facilitated 
by  other  means,  as  to  secure  the  chief  advantage  of  an  actual 
interchange  of  air,  without  the  internal  heat  being  carried  off  by 
the  cause  that  produced  it  ? 

Whatever  prevents  the  radiation  of  heat  from  the  interior  to 
the  exterior  atmosphere  through  the  conducting  agency  of  glass, 
decreases  in  the  same  ratio  the  amount  of  required  heat,  and 
hence,  saves  the  plants  from  being  subjected  to  unnecessary 
excitement.  The  principle  upon  which  a  covering  acts  effi- 


PROTECTION  OF  PLANT-HOUSES  DURING  COLD  NIGHTS.          311 

ciently,  is  that  of  enclosing  a  complete  stratum  of  air  between 
it  arid  the  glass,  this  body  of  air  being  entirely  shut  off  from  the 
surrounding  outer  atmosphere,  as  far  as  may  be  practicable  to 
do  so ;  and  as  air  is  a  bad  conductor  of  heat,  the  warmth  of  the 
interior  is  prevented  from  passing  to  the  exterior  atmosphere,  by 
means  of  direct  radiation  from  the  glass ;  or,  in  other  words,  the 
exterior  atmosphere,  being  prevented  from  coming  in  contact 
with  the  glass,  cannot  absorb  from  the  interior  any  sensible  por- 
tion of  its  heat.  To  secure  this  advantage,  it  will  be  evident 
that  the  covering  must  be  kept  some  distance  from  the  glass, 
and  should  be  on  every  side  where  the  structure  is  formed  of 
glass ;  the  coverings,  in  fact,  should  form  a  complete  case  to  all 
the  glazed  portion  of  the  structure.* 

So  far,  so  good.  As  a  matter  of  protection,  and  nothing  else, 
this  is  all  very  well.  The  advantages  of  such  a  covering  will 
be  obvious  to  every  one ;  and,  as  a  matter  of  protection  alone,  it 
deserves  every  word  that  can  be  said  in  its  favor.  Whether  it 


*  In  the  different  experiments,  it  appears  that  the  cooling  effect  of 
wind  at  different  velocities  on  a  thin  glass  surface,  is  very  nearly  as  the 
square  root  of  the  velocity.  In  these  experiments,  the  velocity  of  the 
air  was  measured  by  the  revolutions  of  the  vanes  of  a  fan.  The  tem- 
perature of  the  air  was  683,  the  time  required  to  cool  the  thermometer 
20°  was  noted  for  every  different  velocity,  and  the  maximum  tempera- 
ture of  the  thermometer  in  each  experiment  was  120°.  In  still  air,  it 
required  5'  4.5"  to  cool  the  thermometer  this  extent,  and  Table  VIII.  in 
the  Appendix  shows  the  time  of  cooling  by  air  in  motion. 

In  consequence  of  the  large  quantity  of  glass  used  in  the  construction 
of  horticultural  buildings,  the  cooling  effect  of  wind  is  of  considerable 
importance.  We  find,  however,  that,  with  an  increased  velocity,  the 
cooling  effect  is  considerably  less  in  proportion,  on  glass,  than  on  metal, 
and  it  will  be  very  much  less  on  window-glass  than  even  what  is  stated 
in  the  table.  As  glass  is  an  extremely  bad  conductor  of  heat,  the 
increased  thickness  which  window-glass  possesses  over  that  which 
forms  the  bulb  of  a  thermometer,  will  make  a  material  difference  in 
the  quantity  of  heat  lost  by  the  abduction  of  the  air,  there  will  be,  as  in 
this  case,  a  greater  difference  between  the  temperature  of  the  external 
and  the  internal  surface.  The  cooling  effect  of  wind,  therefore,  is  not 
near  so  considerable  as  is  generally  supposed  ;  and  the  effect  of  wind  in 
hot-houses  is  very  much  increased  by  open  laps  and  accidental  fissures 
in  the  glazing  of  the  sashes. 

27 


312          PROTECTION  OF  PLANT-HOUSES  DURING  COLD 'NIGHTS. 

can  practicably  be  made  the  means  of  admitting  the  external  air 
into  the  house  at  an  increased  temperature,  and  thereby  creat- 
ing a  motion  in  the  internal  atmosphere,  is  a  question  which,  as 
yet,  we  are  unable  to  prove  from  experience,  although  we  mean 
to  take  an  early  opportunity  of  testing  the  plan  which  we  are 
about  to  describe. 

2.  The  best  material  which  we  have  seen  used  for  this  pur- 
pose is  canvas,  or  any  other  kind  of  strong  coarse  cloth,  painted 
with  two  or  three  coats  of  pitch,  wax,  and  oil  boiled  together,  and 
applied  in  a  warm  state  to  the  cloth ;  this  makes  an  efficient 
and  durable  covering.  Asphalte  felt  is  also  used  extensively 
in  England  and  Germany  for  this  purpose.  This  latter  mate- 
rial is  fixed  on  light  wooden  frames,  about  the  size  of  a  sash,  or 
larger,  as  may  be  found  convenient ;  and  for  covering  frames 
and  pits  it  answers  admirably,  as  it  is  quite  impervious  to  wet, 
and  if  taken  care  of,  will  last  for  some  years.  But  for  covering 
the  roofs  of  large  houses,  we  would  decidedly  prefer  the  cloth, 
which  can  be  more  easily  drawn  off  and  put  on,  and,  if  well 
painted,  will  be  as  impervious  to  air  and  wet,  as  wooden  shut- 
ters, or  asphalte  frames,  and  will  be  cheaper  than  either. 

Suppose,  then,  that  a  glazed  cloth,  of  the  requisite  dimensions, 
is  prepared.  We  would  provide  means  for  securing  it  against 
wind,  by  loops,  etc.,  and  fix  on  parallel  strips  of  wood  over  each 
rafter,  about  nine  inches  from  the  glass.  The  cloth  should  be 
made  to  fit  quite  close  at  the  top,  and  to  reach  the  ground  on 
all  sides  of  the  house,  which,  formed  of  conducting  materials,  or 
side-pieces,  must  be  made  to  fit  closely  over  the  over-lapping 
edge  of  the  upper  one,  and  the  lower  edge  secured  against  the 
admission  of  air.  The  house  is  now  in  a  case,  impervious  both 
to  air  and  water,  and  enclosing  a  stratum  of  air,  which  gradu- 
ally becomes  warmer  than  the  external  atmosphere,  and  effectu- 
ally prevents  the  latter  from  abstracting  the  heat  from  the  inte- 
rior of  the  house.  Then  let  there  be  square  holes  made  along 
the  cloth,  near  the  bottom,  say  one  for  each  alternate  light,  each 
aperture  made  about  ten  inches  square,  and  provided  with  a 
shutter  of  the  same  material,  to  close  it  when  necessary.  All 
these  apertures,  or  any  number  of  them,  may  be  opened,  accord- 


PROTECTION    OF    PLANT-HOUSES    DURING    COLD    NIGHTS.         313 

ing  to  the  wind,  or  other  circumstances  likely  to  affect  the  inter- 
nal atmosphere.  Then  small  apertures  may  be  left  open  in 
different  parts  of  the  house,  during  the  night,  whereby  an  inter- 
change of  the  atmospheric  volume  would  take  place,  without 
exposing  the  plants  to  immediate  contact  with  the  cold  air.  By 
this  plan,  we  conceive  that  direct  benefit  would  accrue  to  the 
plants,  because  the  air  between  the  covering  and  the  glass, 
although  not  cold,  would  nevertheless  be  of  greater  density  than 
that  of  the  house,  and  would  consequently  find  its  way  into  the 
interior,  by  the  ventilators  left  open  for  that  purpose.  This 
would  also  enable  us  to  maintain  a  much  lower  night  tempera- 
ture than  could  possibly  be  otherwise  done,  with  regard  to  the 
safety  of  the  plants,  which  the  fear  of  sudden  changes  during  the 
night,  and  consequent  injury  from  frost,  prevent  from  being 
realized  in  this  changeable  climate. 

It  is  truly  remarkable  how  very  slight  a  covering  is  required 
to  exclude  a  pretty  severe  frost.  "  I  have  often,"  observes  Dr. 
Wells,  "  in  the  pride  of  half-knowledge,  smiled  at  the  means  fre- 
quently employed  by  gardeners  to  protect  tender  plants  from 
cold,  as  it  appeared  to  me  impossible  that  a  thin  mat,  or  any 
such  thin  substance,  could  prevent  them  from  attaining  the  tem- 
perature of  the  surrounding  atmosphere,  by  which  alone,  I  thought 
them  liable  to  be  injured.  But  when  I  had  learned  that  bodies 
on  the  surface  of  the  earth,  become,  during  a  still  and  serene 
night,  colder  than  the  atmosphere,  by  radiating  their  heat  to  the 
heavens,  I  perceived  immediately  a  just  reason  for  the  practice 
which  I  had  before  deemed  useless.  Being  desirous,  however, 
of  acquiring  some  precise  information  on  this  subject,  I  fixed 
perpendicularly  in  the  earth  of  a  grass  plot  four  small  sticks,  and 
over  their  upper  extremities,  —  which  were  six  inches  above  the 
grass,  and  formed  the  corners  of  a  square,  the  sides  of  which 
were  two  feet  long,  —  fixed  a  thin  cambric  handkerchief,  so  as 
to  cover  the  included  space.  In  this  disposition  of  things,  there- 
fore, nothing  existed  to  prevent  the  free  passage  of  air  from  the 
surrounding  grass  to  that  which  was  sheltered  under  the  hand- 
kerchief, except  the  four  small  upright  sticks  supporting  it,  and 
there  was  no  substance  to  radiate  heat  downwards  to  the  grass 
beneath  but  the  cambric  handkerchief.  The  temperature  of  the 


314        PROTECTION    OF    PLANT-HOUSES    DURING   COLD   NIGHTS. 

grass,  which  was  thus  shielded  from  the  sky,  was,  upon  many 
nights  afterwards,  examined  by  me,  and  was  always  found 
higher  than  the  neighboring  grass  which  was  uncovered,  if  this 
was  colder  than  the  air.  When  the  difference  in  temperature 
between  the  air  several  feet  above  the  ground  and  the  unshel- 
tered grass  did  not  exceed  5°,  the  sheltered  grass  was  about  as 
warm  as  the  air.  If  that  difference,  however,  exceeded  5°,  the 
air  was  found  to  be  somewhat  warmer  than  the  sheltered  grass. 
Thus,  upon  one  night,  when  fully  exposed  grass  was  11°  colder 
than  the  air,  the  latter  was  3°  warmer  than  the  sheltered  grass, 
And  the  same  difference  existed  on  another  night,  when  the  air 
was  14°  warmer  than  the  exposed  grass.  One  reason  for  this 
difference,  no  doubt,  was,  that  the  air  which  passed  from  the 
exposed  grass,  by  which  it  had  been  very  much  cooled,  had 
passed  through  that  under  the  handkerchief,  and  deprived  the 
latter  of  part  of  its  heat.  Another  reason  might  be  given,  — 
that  the  handkerchief,  from  being  made  colder  than  the  atmos- 
phere, by  the  radiation  of  its  upper  surface  to  the  heavens,  would 
remit  somewhat  less  to  the  grass  beneath,  than  what  it  received 
from  that  substance.  But  still,  as  the  sheltered  grass,  notwith- 
standing these  drawbacks,  was,  upon  one  night,  as  may  be  seen 
from  the  preceding  account,  8°,  and  upon  another,  11°,  warmer 
than  grass  freely  exposed  to  the  sky,  a  sufficient  reason  was 
now  obtained  for  the  utility  of  a  very  slight  covering,  to  protect 
plants  from  the  influence  of  frost  or  external  cold."  # 

*  As  the  elevation  of  temperature,  induced  by  the  heat  of  summer,  is 
essential  to  the  full  exertion  of  the  energies  of  the  vital  principle,  so  the 
depression  of  temperature,  consequent  upon  intense  cold  nights,  has  been 
thought  to  suspend  the  exertion  of  the  vital  energies  altogether.  But  this 
opinion  is  evidently  founded  on  a  mistake,  as  is  proved  by  the  example 
of  such  plants  as  protrude  their  leaves  and  flowers  in  the  winter  season 
only,  as  well  as  by  the  dissection  of  the  yet  unfolded  bud,  at  different 
periods  of  the  winter,  which  proves  regular  and  progressive  develop- 
ment ;  even  in  the  case  of  such  plants  as  protrude  their  leaves  and 
flowers  in  the  spring  and  summer,  and  in  which,  as  we  have  said,  there 
is  a  gradual,  regular,  and  incipient  development  of  parts,  from  the  time 
of  the  bud's  first  appearance,  till  its  ultimate  opening  in  the  spring.  The 
sap,  it  is  true,  flows  much  less  freely,  but  it  is  not  wholly  stopped.  Du 
Hamel  planted  some  young  trees  in  the  autumn,  cutting  off  all  the 


PROTECTION    OF    PLANT-HOUSES    DURING    COLD    NIGHTS.        315 

We  have  instituted  numerous  experiments  with  the  view  of 
ascertaining  the  capacity  of  various  substances  for  the  protection 
of  plants  and  horticultural  structures,  by  which  we  find  that 
bodies  of  soft  and  open  texture,  —  as  woollen  netting,  thin  cloth, 
&c., —  will,  on  dry,  clear  nights,  afford  an  amount  of  protection 
equal  to  7°  of  frost.  But  if  the  covering  should  become  wet 
before  the  frost  sets  in,  it  will  afford  very  little  protection  to  the 
plants  beneath  it. 

Coarse  cloth,  which  had  been  coated  with  paint,  kept  out  10° 
of  frost,  and  several  kinds  of  plants,  which,  at  the  freezing  point, 
would  suffer  injury,  were  kept  alive  during  the  whole  winter, 
with  the  thermometer  occasionally  indicating  22°  of  frost.  These 
plants  were  frequently  frozen,  but  the  covering  was  never  removed 
during  several  months,  although  the  air  circulated  freely  under- 
neath the  glass. 

In  protecting  plants,  or  glazed  structures  of  any  description,  it 
is  essential  to  observe  that  the  covering  should  always  be  placed 
so  that  a  stratum  of  air  may  always  be  confined  between  the 
covering  and  the  objects  to  be  protected ;  this  is  an  important 
part  of  he  matter,  as,  if  the  covering  be  laid  immediately  on  the 
glass  of  a  frame,  or  green-house,  which  it  is  wished  to  protect, 
the  cold  will  be  conducted  by  the  covering  to  the  glass,  which 
in  turn  will  cool  the  air  beneath  it.  The  covering  should  never 
touch  the  object  to  be  sheltered,  though,  from  what  we  see  around 
us,  this  point  appears  to  be  very  little  attended  to. 

A  covering  of  thin  cloth,  or  woollen  netting,  when  suspended 
in  a  vertical  position  over  trees,  &c.,  will  afford  better  protection 
than  the  same  substance  laid  horizontally  over  the  surface.  In 
this  manner,  wall  trees  are  protected  in  the  British  Isles  from 
spring  frosts,  and  we  have  frequently  seen  the  blossoms  of  peach, 
apricot,  and  pear  trees  completely  uninjured  under  woollen  or 
hair  netting,  when  the  hardiest  trees  of  the  woods  were  nipt 
with  frost,  and  the  tender  vegetables  of  the  garden  were  entirely 

smaller  fibers  of  the  roots,  with  a  view  to  watch  the  progress  of  the  for- 
mation of  new  ones.  At  the  end  of  a  fortnight  he  had  the  plants  all 
taken  up  and  examined,  with  all  possible  care,  to  prevent  injuring  them, 
and  found  that,  when  they  did  not  actually  freeze,  new  roots  were  always 
uniformly  developed. 


316         PROTECTION    OF    PLANT-HOUSES    DURING   COLD   NIGHTS. 

destroyed.  Peaches  and  other  fruit  trees  might  frequently  be 
protected  in  this  way,  and  the  crop,  at  least,  partly  saved,  instead 
of  being,  in  one  single  night,  blasted  for  the  season. 

Common  bass  mats  afford  the  best  and  cheapest  protection  for 
frames  and  small  pits;  but  they  have  the  fault  of  absorbing 
moisture  very  readily  in  wet  weather,  and  then  become  very  bad 
protection.  They  should  never  be  laid  on  the  glass  in  a  wet 
state,  as  they  are  sure  to  do  more  injury  than  good.  We  have 
found  it  an  excellent  method,  in  covering  frames  and  small 
houses  with  mats,  to  have  a  thin  water-proof  covering  to  lay 
over  the  mats,  which  not  only  prevents  the  escape  of  the  con- 
fined air,  but  also  keeps  the  mats  always  dry,  and  thus,  one  of 
the  very  best  protectors  is  obtained. 

Large  structures  are  more  difficult  to  cover  than  pits,  and  the 
difficulty  which  thus  presents  itself  has,  in  general,  prevented 
every  attempt  to  overcome  it.  We  have  seen  various  plans  put 
in  operation,  besides  that  which  we  have  already  described ;  all 
more  or  less  effectual.  The  difficulty  of  getting  common  rollers 
to  work  in  frosty  weather  has  made  them  all  but  useless,  in  the 
protection  of  hot-houses  by  rolling  blinds,  or  screens  of  oil-cloth. 
Nevertheless,  this  plan  is  not  only  an  effectual  one,  but  one 
which  is  cheap  and  easily  adopted.  And  the  cloth  can  be  drawn 
off,  in  the  mornings,  and  spread  out  to  dry  on  the  snow,  or  hung 
on  a  fence,  during  the  day.  When  the  time  comes  for  covering 
at  night,  it  might  be  so  arranged  as  to  be  drawn  up  by  cords 
passing  through  a  pulley  at  each  end  of  the  house.  We  have 
succeeded  in  arrangements  of  this  kind  ;  and  the  saving  of  fuel 
in  a  severe  winter,  with  the  certainty  of  the  plants, being  safe 
from  injury,  either  from  frost  or  from  fire,  is  ample  compensation 
for  the  trouble  which  it  costs. 

Whatever  kind  of  object  it  is  wished  to  protect,  whether  a 
house  or  a  plant,  the  protector  should  always  be  at  least  one 
foot  from  it.  A  considerable  difference  of  temperature  is  always 
observed,  on  still  and  serene  nights,  between  bodies  sheltered 
from  the  sky  by  substances  touching  them,  and  similar  bodies 
which  were  sheltered  by  a  substance  a  little  above  them.  "I 
found,  for  example,"  says  Dr.  Wells,  "  upon  one  night,  that  the 
warmth  of  grass  sheltered  by  a  cambric  handkerchief,  raised  a 


PROTECTION    OF    PLANT-HOUSES    DURING   COLD   NIGHTS.         317 

few  inches  in  the  air,  was  3°  greater  than  a  neighboring  piece 
of  grass,  which  was  sheltered  by  a  similar  handkerchief,  which 
was  actually  in  contact  with  it.  On  another  night  the  difference 
between  the  temperatures  of  the  two  portions  of  grass,  sheltered 
in  the  same  manner  as  the  two  above  mentioned,  from  the  influ- 
ence of  the  sky,  was  4°.  Possibly,"  says  he,  "  experience  has 
long  ago  taught  gardeners  the  superior  advantages  of  defending 
tender  plants  from  the  cold  of  clear  and  calm  nights,  by  means 
of  substances  not  directly  touching  them,  though  I  do  not  recol- 
lect ever  having  seen  any  contrivance  for  keeping  mats,  and  such 
like  bodies,  at  a  distance  from  the  plants  which  they  were  meant 
to  protect."  We  know  this  to  be  a  fact ;  for  gardeners  seldom 
take  any  thought  whether  the  plant  is  protected  or  not,  provid- 
ing it  be  covered,  with  mats  or  something  else,  from  the  external 
atmosphere. 

Straw,  and  corn  stalks,  afford  good  protection  to  trees  and  half 
hardy  shrubs,  when  properly  arranged,  so  that  the  covering  may 
be  water-tight.  The  air  that  lodges  among  the  straw,  and  in 
the  interstices  of  the  stalks,  keeps  the  plant  within,  always  at  a 
regular  temperature,  and  prevents  sudden  freezing  and  thawing, 
which  prove  the  destruction  of  tender  plants. 

Bodies,  however,  capable  of  absorbing  heat  during  the  day, 
and  parting  with  it  at  night,  when  the  temperature  of  the  atmos- 
phere falls,  are  also  useful  as  a  means  of  protecting  plants,  &c. 
Among  such  bodies  may  be  classed  the  walls  of  houses,  which 
may  be  regarded  useful  in  two  ways  ;  namely,  by  the  mechani- 
cal shelter  they  afford  against  cold  winds,  and  by  giving  out 
the  warmth,  during  the  night,  which  they  had  absorbed  during 
the  day.  It  appears,  however,  that  on  clear  and  calm  nights, 
those,  on  which  plants  frequently  receive  much  injury  from  cold, 
walls  must  be  beneficial  in  another  way;  namely,  by  preventing, 
in  part,  the  loss  of  heat,  which  the  plants  would  sustain  from 
radiation,  if  they  were  fully  exposed  to  the  sky.  The  following 
experiment  was  made  by  Dr.  Wells,  for  the  purpose  of  deter- 
mining the  justness  of  this  opinion.  A  cambric  handkerchief 
having  been  placed,  by  means  of  two  upright  sticks,  perpendicu- 
larly to  a  grass  plot,  and  at  right  angles  to  the  course  of  the  air, 
a  thermometer  was  laid  upon  the  grass  close  to  the  lower  edge 


318          PROTECTION  OF  PLANT-HOUSES  DURING  COLD  NIGHTS. 

of  the  handkerchief  on  its  windward  side.  The  thermometer 
thus  situated  was,  for  several  nights,  compared  with  another 
lying  on  the  same  grass  plat,  but  on  a  part  of  it  fully  exposed 
to  the  sky.  On  two  of  these  nights,  the  air  being  clear  and 
calm,  the  grass  close  to  the  handkerchief  was  found  to  be  four 
degrees  warmer  than  the  fully  exposed  grass ;  on  a  third  night 
the  difference  was  six  degrees.  An  analogous  fact  is  men- 
tioned by  Gersten,  who  says  that  a  horizontal  surface  is  more 
abundantly  dewed  than  one  which  is  perpendicular  to  the 
ground. 

Snow  forms  an  excellent  covering,  and  seems  to  be  a  provis- 
ion of  nature  for  the  protection  of  many  tender  roots  and  plants 
which  would  otherwise  perish.  Its  usefulness  as  a  plant-pro- 
tector may  be  disputed,  from  the  fact  of  their  tops  being  exposed 
to  the  influence  of  the  atmosphere,  while  their  roots  and  lower 
parts  only  are  protected.  In  reply  to  this,  however,  we  may 
observe,  that  it  prevents  the  occurrence  of  the  cold,  which  bodies 
on  the  earth  acquire  in  addition  to  that  of  the  atmosphere,  by 
the  radiation  of  their  heat  to  the  heavens,  in  still  and  clear 
nights.  The  cause,  indeed,  of  this  additional  cold,  does  not 
constantly  operate,  but  its  presence  during  only  a  few  hours, 
might  effectually  destroy  plants  which  now  pass  unhurt  through 
the  winter.  Again,  as  things  are,  while  low-growing  vegetable 
productions  are  prevented,  by  the  covering'of  snow,  from  becom- 
ing colder  than  the  atmosphere,  in  consequence  of  their  own 
radiation,  the  parts  of  trees  and  tall  shrubs  which  rise  above  the 
snow  are  little  affected  by  cold  from  this  cause ;  for  their  outer- 
most twigs,  now  that  they  are  destitute  of  leaves,  are  much 
smaller  than  the  thermometer  suspended  by  us  in  the  air,  which, 
in  this  situation,  seldom  became  more  than  two  degrees  colder 
than  the  atmosphere.  The  large  branches,  too,  which,  if  fully 
exposed  to  the  sky,  would  become  colder  than  the  extreme  parts, 
are  in  a  great  degree  sheltered  by  them,  and,  in  the  last  place, 
the  trunks  are  sheltered  both  by  the  larger  and  smaller  parts, 
not  to  speak  of  the  heat  they  derive  by  conduction  through  the 
roots,  from  the  earth  kept  warm  by  the  snow.  In  a  similar  man- 
ner is  partly  to  be  explained  the  way  in  which  a  layer  of  straw 


PROTECTION  OF  PLANT-HOUSES  DURING  COLD  NIGHTS.  319 

or  earth  preserves  vegetable  matters  in  the  fields  from  the  inju- 
rious influence  of  cold  during  severe  winters.  * 

When  frames  and  such  places  are  covered  with  snow,  it 
should  be  allowed  to  remain  on  till  it  melts  away  by  the  influ- 
ence of  the  atmosphere.  In  like  manner,  trees  and  shrubs 
should  never  have  the  snow  drawn  from  their  branches,  during 
snow  storms,  except  where  the  branches  are  likely  to  be  broken 
down  by  the  weight  of  snow  lying  upon  them.  Snow  is  not 
only  the  best,  but  also  the  most  natural,  covering  during  the 
winter  months. 

*  That  the  warmth  of  the  soil  acts  as  a  protection  to  plants  may  be 
easily  understood.  A  plant  is  penetrated  in  all  directions  by  innumera- 
ble microscopic  air-passages  and  chambers,  so  that  there  is  a  free  com- 
munication between  its  extremities.  It  may,  therefore,  be  conceived 
that,  if,  as  necessarily  happens,  the  air  inside  the  plant  is  in  motion,  the 
effect  of  warming  the  air  in  the  roots  will  be  to  raise  the  temperature 
of  the  whole  individual,  and  the  same  is  true  of  its  fluids.  Now,  when 
the  temperature  of  the  soil  is  raised  to  50°  at  noonday,  by  the  force  of 
the  solar  rays,  it  will  retain  a  considerable  part  of  that  warmth  during 
the  night ;  but  the  temperature  of  the  air  may  fall  to  such  a  degree,  that 
the  excitability  of  a  plant  would  be  too  much  and  too  suddenly  impaired, 
if  it  acquired  the  coldness  of  the  medium  surrounding  it.  This  is  pre- 
vented by  the  warmth  communicated  to  the  general  system,  from  the 
soil  through  the  roots,  so  that  the  lowering  of  the  temperature  of  the 
air  by  radiation  during  the  night,  is  unable  to  affect  plants  injuriously 
in  consequence  of  the  antagonist  force  exercised  by  the  heated  soil. 


SECTION    VII. 

GENERAL    REMARKS    ON     THE     MANAGEMENT    OF     THE 
ATMOSPHERE     OF     HOT-HOUSES. 

1.  ONE  of  the  most  prevalent  errors,  and  one  of  very  consid- 
erable importance,  consists  in  reversing  the  natural  condition 
of  the  atmosphere  in  regard  to  the  artificial  regulation  of  the 
temperature  during  the  night.  The  artificial  climate  is  not 
rendered  natural  by  adjusting  it  to  the  heat  and  light  of  the  sun. 
In  cloudy  weather,  and  during  night,  the  artificial  atmosphere 
is  kept  hot  by  fires,  and  by  excluding  the  external  air;  while,  in 
clear  days  and  during  sunshine,  fires  are  left  off,  or  allowed  to 
decline,  the  external  atmosphere  is  admitted,  and  the  internal 
atmosphere  is  reduced  to  the  temperature  of  the  air  without. 
As  heat  in  nature  is  the  result  of  the  shining  of  the  sun,  it  fol- 
lows that  when  there  is  most  light  there  is  most  heat ;  but  the 
practice  in  managing  hot-houses  is  generally  the  reverse. 

"A  gardener,"  observes  Knight,  "generally  treats  his  plants  as 
he  would  wish  to  be  treated  himself,  and  consequently,  though 
the  aggregate  temperature  of  his  house  be  nearly  what  it  ought 
to  be,  its  temperature  during  the  night,  relatively  to  that  of  the 
day,  is  almost  always  too  high. 

"  It  is  very  doubtful  if  any  point  in  exotic  horticulture  is  less 
attended  to  than  that  which  is  involved  in  this  question.  We 
are  too  apt  to  forget  that  plants  not  only  have  their  periodical 
rest  of  winter  and  summer,  but  they  have  also  their  diurnal 
periods  of  repose.  Night  and  its  accompanying  refreshments 
are  just  as  necessary  to  them  as  to  animals.  In  all  nature,  the 
temperature  of  night  falls  below  that  of  day,  and  thus,  the  great 
cause  of  vital  excitement  is  diminished,  perspiration  is  stopped, 
and  the  plant  parts  with  none  of  its  aqueous  particles,  although 
it  continues  to  imbibe  by  all  its  green  surface  as  well  as  by  its 
roots.  The  processes  of  assimilation  are  suspended.  No  diges- 


THE    ATMOSPHERE    OF   HOT-HOUSES.  321 

tion  of  food  and  conversion  of  it  into  organized  matter  takes 
place,  and  instead  of  decomposing  carbonic  acid  by  the  extrica- 
tion of  oxygen,  they  part  with  carbonic  acid,  and  rob  the  atmos- 
phere of  its  oxygen,  thus  deteriorating  the  air  at  night.  It  is, 
therefore,  most  important  that  the  temperature  of  glass-houses 
of  every  kind  should,  under  all  circumstances  whatever,  be 
lower  during  the  night  than  the  minimum  temperature  of  the 
day ;  and  this  ought  to  take  place  to  a  greater  extent  than  is 
generally  imagined  among  practical  gardeners. 

"  Plants,  it  is  true,  thrive  well,  and  many  species  of  fruit  attain 
their  greatest  state  of  perfection  in  some  situations  within  the 
tropics,  where  the  temperature  in  the  shade  does  not  vary  in 
the  day  and  night  more  than  seven  or  eight  degrees;  but  in 
these  climates  the  plant  is  exposed  during  the  day  to  the  full 
blaze  of  the  tropical  sun,  and  early  in  the  night  it  is  regularly 
drenched  with  heavy  wetting  dews,  and,  consequently,  it  is  very 
differently  circumstanced  in  the  day  and  night,  though  the  tem- 
perature of  the  air  in  the  shade,  at  both  periods,  be  very  nearly 
the  same.  I  suspect,"  continues  Knight,  "  that  a  large  por- 
tion of  the  blossoms  of  the  cherry  and  other  fruit  trees  in  the 
forcing-house  often  prove  abortive,  because  they  grow  in  too  high 
and  too  uniform  a  temperature.  I  have  been  led,"  he  says, 
"  during  the  last  three  years,  to  try  the  effects  of  keeping  up  a 
much  higher  temperature  during  the  day  than  during  the  night. 
As  early  in  the  spring  as  I  wished  the  blossoms  of  my  peach 
trees  to  unfold,  my  house  was  made  warm  during  the  middle  of 
the  day,  but,  towards  night,  it  was  suffered  to  cool,  and  the 
trees  were  then  sprinkled,  by  means  of  a  large  syringe,  with 
clear  water,  as  nearly  at  the  temperature  as  that  which  rises 
from  the  ground  as  I  could  obtain  it,  and  no  artificial  heat  was 
given  during  the  night,  unless  there  appeared  a  prospect  of  frost. 
Under  this  mode  of  treatment,  the  blossoms  advanced  with  very 
great  vigor,  and,  when  expanded,  were  of  a  larger  size  than  I 
had  ever  before  seen  on  the  same  varieties. 

"  Another  ill  effect  of  high  night  temperature  is,  that  it  exhausts 
the  excitability  of  the  tree  much  more  rapidly  than  it  promotes 
the  growth,  or  accelerates  the  maturation,  of  the  fruit,  which 
is,  in  consequence,  ill  supplied  with  nutriment  at  the  period  of 


322  GENERAL   REMARKS    ON    THE    MANAGEMENT 

its  ripening1,  when  most  nutriment  is  probably  wanted.  The 
Muscat  of  Alexandria  grapes,  and  some  other  late  grapes,  are 
often  seen  to  wither  upon  the  branch  in  a  very  imperfect  state 
of  maturity,  and  the  want  of  richness  and  flavor  in  other  forced 
fruit  is,  we  are  very  confident,  often  attributable  to  the  same 
cause.  There  are  few  peach  houses  or  graperies  in  this  coun- 
try in  which  the  night  temperature  does  not  exceed,  during  the 
months  of  April  and  May,  that  of  the  warmest  valleys  of 
Jamaica,  in  the  hottest  period  of  the  year.  And  there  are  prob- 
ably as  few  hot-houses  in  which  the  trees  are  not  more  strongly 
stimulated  by  the  close  and  damp  air  of  the  night,  than  by  the 
temperature  of  the  dry  air  of  the  noon  of  the  following  day. 
The  practice  which  occasions  this  cannot  be  right;  it  is  in 
direct  opposition  to  nature."^ 

We  have  fully  satisfied  ourselves  that  a  high  night  temperature 
is  injurious  to  plants  of  any  description,  kept  under  glass,  and 
that  green-house  plants  not  only  expand  their  flowers  more  per- 
fectly, but  continue  much  longer  in  bloom,  when  the  temperature 
of  the  house  is  reduced  at  night  by  the  admission  of  air  or  other- 
wise. In  like  manner,  fruits  are  not  only  better  flavored,  —  a 
fact  generally  admitted,  —  but  also  better  colored,  and  more  per- 
fect in  form,  by  a  low  temperature  at  night.  On  the  other 
*  hand,  too  much  air  is  generally  admitted  during  the  day. 

There  is  no  doubt  that  gardeners  frequently  err  in  admitting 
the  external  air  into  their  hot-houses,  etc.,  during  the  day,  par- 
ticularly in  bright  weather;  and  this  error  is  so  common  as  to 
form  a  portion  of  regular  practice.  We  have  seen  graperies 
and  green-houses  fully  exposed  to  the  parching  winds  of  a  sum- 
mer day,  without  screen  or  shelter;  while  the  plants  subjected 
to  this  treatment  plainly  indicated,  by  their  appearance,  its  inju- 
rious effects.  The  climate  of  this  country  is  so  different  in 
respect  to  its  atmosphere  during  the  day,  from  that  of  Britain, 
we  are  too  apt  to  follow  the  practice  of  that  country,  where  this 
practice  is  also  carried  to  too  great  extent.! 

*  Loudon's  Encyclopedia  of  Gardening. 

f  The  climate  of  the  British  Isles,  relatively  to  others  in  the  same  lati- 
tude, is  temperate,  humid,  and  variable.  The  moderation  of  its  temper- 
ature and  its  humidity  are  owing  to  its  being  surrounded  by  water, 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  323 


The  striking  difference  which  is  exhibited  between  our  con- 
servatories and  green-houses  in  this  country,  and  those  of  Eng- 
land, is  not  so  much  owing  to  the  existing  peculiarities  of  cli- 
mate, as  to  the  methods  of  practice  adopted  by  the  gardeners 
themselves  in  the  management  of  the  atmosphere  of  their 
houses.  However  costly  and  faultlessly  a  conservatory,  a  hot- 
house, or  a  grapery,  may  be  constructed,  the  whole  success  of 
the  structure  depends  upon  the  subsequent  management  of  its 
atmosphere. 

The  imitation  of  warm  climates  in  winter,  for  the  purpose  of 
preserving  tender  plants,  must  not  be  confounded  with  the  arti- 
ficial climate  created  in  a  hot-house  for  the  purpose  of  forcing 
or  accelerating  foreign  or  native  productions.  As  two  different 
objects  are  sought  for,  different  courses  of  procedure  must  be 
adopted.  All  that  is  necessary  for  the  preservation  of  green- 
house plants,  is  to  keep  the  atmosphere  at  night  a  few  degrees 
above  the  freezing  point ;  and,  indeed,  if  a  proper  attention  be 
paid  to  the  plants,  so  as  to  avoid  an  excess  of  moisture,  there  is 
scarcely  any  kind  of  what  are  generally  termed  hot-house  plants, 
that  will  not  thrive  well  enough  under  similar  treatment.  We 
have  often  allowed  our  plant-houses  to  fall  below  the  freezing 
point  in  very  severe  nights;  and  when  long  and  continued  frosts 
set  in,  the  plant-houses  should  be  gradually  inured  to  bear  even 
a  few  degrees  of  frost  below  32° ;  and  this  the  plants  will  do 
without  injury,  if  they  be  kept  in  a  proper  condition.  When 
the  external  atmosphere  is  dry  and  mild,  air  should  be  admitted 
freely  to  the  green-house  during  winter,  but  closed  early  in  the 

which,  being  less  affected  by  the  sun  than  the  earth,  imbibes  less  heat 
in  summer,  and,  from  its  fluidity,  is  less  early  cooled  in  winter.  As  the 
sea  on  the  coasts  of  Britain  never  freezes,  its  temperature  must  always 
be  above  33°  or  34°  ;  and  hence,  when  air  from  the  polar  regions,  at  a 
much  lower  temperature,  passes  over  it,  that  air  must  be  in  some  degree 
heated  by  the  radiation  of  the  water.  On  the  other  hand,  in  summer, 
the  warm  currents  of  air  from  the  south  necessarily  give  out  part  of 
their  heat  in  passing  over  a  surface  so  much  lower  in  temperature. 
The  variable  nature  of  its  climate  is  chiefly  owing  to  the  unequal 
breadth  of  watery  surface  which  surrounds  it,  —  on  one  side  a  channel 
of  a  few  leagues  in  breadth,  on  the  other,  the  broad  Atlantic  Ocean.  — 
[London's  Ency.  of  Gard.] 


324        GENERAL  REMARKS  ON  THE  MANAGEMENT 

afternoon,  so  as  to  preserve  a  portion  of  the  warmth  generated 
by  the  sun's  rays  within  the  house,  to  maintain  a  slight  degree 
of  heat  in  the  house  before  the  heating  apparatus  is  set  to  work. 

The  accelerating,  or  forcing,  of  the  vegetables  and  fruits  of 
temperate  climates  into  a  state  of  premature  production  is  some- 
what different,  and  more  difficult,  than  the  preservation  of  plants 
during  winter.  The  constitutions  of  the  various  fruit-bearing 
plants,  as  vines,  &c.,  require  atmospheres  of  different  tempera- 
ture and  moisture,  and  their  success  is  dependent  upon  many 
contingent  circumstances,  which  never  occur  in  the  mere  preser- 
vation of  green-house  plants. 

The  two  principal  methods  of  accelerating  fruits  in  hot- 
houses are,  by  planting  them  permanently  in  borders  prepared 
for  them,  and  by  planting  in  tubs  and  large  pots  ;  and  keeping 
a  succession  of  plants  thus  prepared,  every  year,  to  supply  the 
places  of  those  which  had  become  unfruitful  by  the  effects  of 
forcing  and  producing  a  heavy  crop  of  fruit. 

The  first  of  these  methods  has  long  been  practised,  and  is, 
undoubtedly,  the  best  for  permanent  crops,  as  more  fruit  can  be 
produced  in  a  house  by  this  method  than  by  the  potting  system. 
When  once  planted  out,  however,  and  growing  under  the  glass, 
they  cannot  be  removed  from  the  house,  and,  consequently,  are 
dependent  upon  the  cultivator  for  the  elements  of  consumption, 
air  and  water.  The  grand  effect  is  produced  by  heat,  and  the 
great  aim  is  to  supply  just  as  much  as  will  harmonize  with  the 
light  afforded  by  the  sun,  and  the  peculiar  condition  under  which 
the  plants  exist.  All  the  operations  must  be  natural  and  grad- 
ual, and  a  good  cultivator  will  always  follow  the  dictates  and 
example  of  the  natural  world.  He  will  never  be  anxious  to  force 
things  on  too  rapidly,  —  a  very  common  error,  and  a  frequent 
cause  of  failure ;  he  will  likewise  be  careful  to  guard  against 
sudden  checks,  either  by  a  sudden  decrease  of  temperature,  or 
the  reverse  ;  but  he  will  endeavor  to  continue  the  natural  course 
of  vegetation  uninterruptedly  through  foliation,  inflorescence,  and 
fructification. 

The  skilful  balancing  of  the  temperature  and  moisture  of  the 
air,  in  cultivating  the  different  kinds  of  fruits  in  forcing-houses, 
and  the  just  adaptation  of  the  various  seasons  of  growth  and 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  325 

maturity,  constitute  the  most  complicated  and  difficult  part  of 
the  gardener's  art.  There  is  some  danger  in  laying  down  any 
general  rules  on  this  subject,  so  much  depends  upon  the  pecu- 
liarities of  the  kind  under  cultivation,  and  the  endless  train  of 
considerations  connected  with  the  process  of  forcing. 

The  following  rules,  however,  may  be  safely  stated,  as  deserv- 
ing especial  attention  from  the  gardener  in  charge  of  hot-houses  : 

1.  Moisture  is  most  required  in  the  atmosphere  by  plants 
when  they  first  begin  to  grow,  and  least  when  their  periodical 
growth  is  completed. 

2.  The  quantity  of  atmospheric  moisture  required  by  plants 
is,  cceteris  paribus,  in  inverse  proportion  to  the  distance  from  the 
equator  of  the  countries  which  they  naturally  inhabit. 

3.  Plants  with  annual  stems  require  more  than   those  with 
ligneous  stems. 

4.  The  amount  of  moisture  in  the  air  most  suitable  to  plants 
at  rest,  is  in  inverse  proportion  to  the  quantity  of  aqueous  matter 
they,  at  that  time,  contain.     Hence  the  dryness  required  in  the 
atmosphere,  by  succulent  plants,  when  at  rest. 

Moisture  in  the  atmosphere,  then,  is  absolutely  necessary  to 
all  plants,  when  they  are  in  a  state  of  rapid  growth,  partly  be- 
cause it  prevents  the  action  of  perspiration  becoming  too  violent, 
as  it  always  does  in  a  high  and  dry  atmosphere,  and  partly 
because,  under  such  circumstances,  a  considerable  quantity  of 
aqueous  food  is  absorbed  from  the  atmosphere,  in  addition  to 
that  drawn  from  the  soil  by  the  roots. 

Excessive  moisture  is  injurious  to  vegetables  in  winter,  when 
their  digestive  and  decomposing  powers  are  feeble,  and  evapora- 
tion from  the  soil  should  rather  be  intercepted  than  otherwise, 
except  when  the  atmosphere  is  dried  to  an  unhealthy  degree, 
by  the  use  of  fire  heat. 

One  of  the  causes  of  the  Dutch  method  of  winter-forcing  is, 
undoubtedly,  their  avoiding  the  necessity  of  winter  ventilation, 
by  intercepting  the  excessive  vapor  that  rises  from  the  soil,  and 
would  otherwise  mix  with  the  air.  For  this  purpose  they  inter- 
pose screens  of  oiled  paper  between  the  earth  and  the  air  of  their 
houses ;  and  in  their  pits  for  vegetables,  they  cover  the  surface 
of  the  ground  with  the  same  oiled  paper,  by  which  means  vapor 


326        GENERAL  REMARKS  ON  THE  MANAGEMENT 

is  effectually  intercepted,  and  the  atmosphere  preserved  from 
excessive  moisture. 

The  difficulty  of  keeping  succulent  plants  in  damp  cellars, 
during  winter,  is  also  owing  to  the  same  cause.  Moisture, 
without  a  sufficiency  of  light  to  enable  plants  to  decompose  it, 
quickly  destroys  them. 

On  the  other  hand,  the  difficulty  of  keeping  up  that  necessary 
degree  of  humidity  in  the  atmosphere  of  a  dwelling  room,  dur- 
ing the  summer  months,  is  the  cause  of  the  unhealthiness  of 
plants  kept  in  them  ;  and  the  fact  of  their  position  being  gener- 
ally in  the  window,  where  there  is  always  a  current  of  air  from 
without,  during  the  day,  contributes,  in  a  great  measure,  to 
exhaust  the  plants  of  their  contained  moisture,  and  then  they 
gradually  decline.  Could  the  atmosphere  around  them  be  kept 
sufficiently  moist,  with  plenty  of  light,  there  is  no  reason  why 
they  should  not  thrive  as  well  as  in  the  green-house. 

We  have  already  alluded  to  the  injurious  effects  of  maintain- 
ing a  high  temperature  in  green-houses  and  conservatories  dur- 
ing winter.  If  we  look  over  the  different  climates  of  the  world, 
we  shall  find,  that  in  each  there  is  a  season  of  growth,  and  a 
season  in  which  vegetation  is  more  or  less  suspended,  and  that 
these  periodically  alternate  with  the  same  regularity  as  our 
summer  and  winter.  I  do  not  know  that  in  nature  there  is  any 
exception  to  this  rule ;  for  even  in  the  Tierra  Templada  of  Mex- 
ico, where,  it  is  said,  that,  at  the  height  of  4000  to  5000  feet, 
there  constantly  reigns  the  genial  climate  of  spring,  which  does 
not  vary  more  than  8°  or  9°  of  temperature,  —  intense  heat  and 
excessive  cold  being  alike  unknown,  —  the  mean  temperature 
varying  from  68°  to  70°;  we  cannot  suppose  that,  even  in 
that  favored  region,  a  season  of  repose  is  wanting;  for  it  is 
difficult  to  conceive  how  plants  can  exist,  any  more  than  animals, 
in  a  season  of  incessant  excitement.  Indeed,  it  is  pretty  evident 
that  these  countries  have  periods  when  vegetation  ceases,  for 
Xalapa  belongs  to  the  Tierra  Templada,  and  we  know  that  the 
Ipomea  purga,  an  inhabitant  of  its  woods,  dies  down  annually, 
like  our  native  Convolvuli. 

From  what  has  already  been  said  on  this  subject,  it  is  evident 
that  the  natural  resting  of  plants  from  growth  is  a  most  impor- 


OF    THE    ATMOSPHERE    OF    HOT-HOUSES.  327 

tant  phenomenon,  of  universal  occurrence,  and  that  it  takes  place 
equally  in  the  hottest  and  in  the  coldest  regions.  It  is,  there- 
fore, a  condition  necessary  to  the  well-being  of  a  plant,  not  to 
be  overworked,  under  any  circumstances  whatever ;  and  there 
cannot  be  any  good  gardening  where  this  is  not  attended  to,  in 
the  management  of  plants  under  glass.  Rest  is  effected  in  two 
ways ;  either  by  a  very  considerable  lowering  of  temperature, 
or  by  a  degree  of  dryness  under  which  vegetation  cannot  be 
sustained. 

In  treating  on  the  various  conditions  of  the  atmosphere,  and 
its  effects  on  vegetation,  we  have  already  sufficiently  explained 
these  influences ;  which  renders  it  unnecessary  to  recapitulate 
them  in  this  place.  In  practice  we  find  that  the  effects  of  a 
very  dry  atmosphere  are,  necessarily,  an  inspissated  state  of  the 
sap  of  the  plant,  and  this,  in  all  cases,  —  if  not  carried  to  an 
injurious  extent,  —  leads  to  the  formation  of  blossom-buds,  and 
of  fruit.  This  influence,  however,  must  be  controlled  by  the 
cultivator,  otherwise  it  will  lead  to  inevitable  failure,  as  the  sap 
of  the  plant  may  be  so  much  dried  up  as  to  prevent  its  accumu- 
lation in  sufficient  quantity,  in  the  smaller  branches,  to  form 
fruit  buds.  It  is,  nevertheless,  true,  that  a  low  temperature, 
under  the  influence  of  much  light,  by  retarding  and  diminishing 
the  expenditure  of  the  sap  in  growing  plants,  produces  nearly 
similar  effects,  and  causes  an  early  appearance  of  fruit. 

All  the  operations  may  be  very  essentially  influenced  by  these 
facts,  when  they  are  fully  understood  to  the  cultivator,  and,  by 
a  skilful  alteration  of  the  periods  of  rest,  we  are  enabled  to 
break  in  upon  the  natural  habits  of  plants,  and  to  invert  them 
so  completely,  that  the  flowers  and  fruits  of  summer  may  be 
brought  to  perfection  at  the  opposite  season  of  the  year. 

By  carrying  out  these  principles,  we  have,  for  several  years, 
succeeded  in  fruiting  grape-vines  in  the  months  of  March  and 
April,  without  any  extraordinary  degree  of  excitability  being 
exercised  at  any  period  of  their  growth.  The  whole  secret  of 
success  consists  in  preparing  the  plants  the  preceding  season, 
by  ripening  their  wood  at  an  early  period  of  the  season,  and  ex- 
posing them  to  such  an  amount  of  heat  and  dryness  as  can  be  ob- 
tained by  presenting  them,  unwatered,  to  the  influence  of  the  sun, 


328  GENERAL   REMARKS,    ETC. 

at  an  early  period  of  summer ;  then,  after  the  leaves  have  ripened, 
keep  them  as  cool  as  possible  for  some  time ;  thus  causing  a 
sufficient  accumulation  of  excitability  by  the  end  of  October, 
instead  of  the  following  month  of  May,  at  which  period  the  fruit 
will  be  ripe. 


. 

SECTION    VIII. 

VENTILATION     WITH     FANS. 

IN  a  preceding  part  of  this  work,  [see  Part  II.,  Sec.  V.]  we  have 
described  a  method  of  warming  hot-houses  practised  in  Ger- 
many, in  which  a  fan  is  used  as  a  means  of  propelling  the 
heated  air  into  the  apartments  required  to  be  warmed,  and  by 
which  the  volume  of  air  to  be  heated  is  drawn  from  the  external 
atmosphere.  As  an  auxiliary  to  a  heating  apparatus,  however, 
the  complicated  arrangements  of  this  machine,  the  cost  of  its 
construction,  and  the  expense  and  trouble  of  working  it,  must 
ever  continue  to  prevent  its  adoption  as  a  method  of  warming 
horticultural  buildings,  however  extensive  they  may  be.  But  as 
an  auxiliary  of  ventilation,  and  as  a  means  of  creating  that  con- 
tinual motion  in  the  air,  which  some  cultivators  so  much  admire, 
it  is  undoubtedly  superior  to  all  other  methods. 

Fans  are  so  common  as  to  require  very  little  description.  The 
kind  of  machine  generally  used  for  this  purpose  is  merely  a 
light  circular  kind  of  wheel,  composed  of  as  many  vanes  or  blades 
as  the  size  will  admit.  By  the  constant  revolution  of  this  wheel, 
a  movement  is  created  in  the  atmosphere,  which  causes  a  change 
in  the  position  of  the  atomic  particles  of  the  atmosphere  of  the 
room  in  which  it  is  at  work ;  but  does  not,  as  some  suppose, 
tend  to  its  equalization. 

Fans  are  of  two  kinds,  and  have  different  methods  of  action. 
The  one  is  termed  blowing  fans  ;  the  other,  exhausting,  or  suction 
fans.  In  the  first  case,  the  air  in  the  house  is  driven  outwards 
from  the  fan,  or  blown  away ;  in  the  other,  it  is  drawn  towards  it. 
It  will  appear  evident,  however,  that,  in  applying  this  machine 
to  the  creation  of  a  movement  in  the  atmosphere  of  a  hot-house, 
various  requisites  must  be  had,  namely,  a  moving  power,  con- 
stantly and  steadily  acting,  and  completely  under  control ;  and 
when  it  is  to  be  applied  to  night  ventilation  and  motion,  which 
appears  to  us  the  most  adaptable  use  to  which  it  can  be  applied 


330  VENTILATION    WITH    FANS. 

in  relation  to  any  kind  of  horticultural  structures,  then  a  supply 
of  warmed  air  must  be  kept  up  by  means  of  the  heating  appa- 
ratus, and  a  channel  of  conduction  for  the  vitiated  air  to 
escape  by. 

In  places  where  the  mechanical  power  for  moving  a  fan  can 
be  easily  obtained,  this  machine  may  be  turned  to  excellent 
advantage.  The  question,  therefore,  is  not  as  to  the  adaptability 
of  the  machine,  but  as  to  the  means  of  working  it  so  as  to  bring 
it  within  the  reach  of  hot-house  adaptation,  at  a  cost  which 
would  justify  us  in  recommending  it. 

There  are  various  points  to  be  considered  in  relation  to  draw- 
ing in  fresh,  and  expelling  foul,  air  from  a  hot-house,  namely,  that 
we  must  not  only  expel  the  vitiated  air  from  the  house,  but  we 
must  introduce  pure  air  into  its  place  ;  and  that  pure  air  must 
be  warmed  before  it  is  introduced.  We  have  heard  and  read  a 
good  deal  about  this  and  the  other  method  of  introducing  warm 
air  into  a  hot-house ;  and,  in  theory,  many  of  these  notions  are 
very  plausible,  but  when  we  come  to  apply  them  to  practice, 
they  are  entire  failures. 

The  principal  objects  to  be  obtained  by  an  efficient  system  of 
night  ventilation  may  be  classed  as  follows  :  — 

1.  The  expulsion  of  a  certain  quantity  of  vitiated  air,  in  a 
certain  time,  from  the  whole  volume  contained  in  the  house ; 
and,  as  the  impure  air  rises  by  rarefaction  to  the  upper  regions 
of  the  house,  means  must  be  provided  to  carry  it  away,  with- 
out creating  counter-currents,  or  admitting  any  cold  air,  by  the 
channels  of  conduction  thus  made. 

2.  A  quantity  of  air  must  be  introduced  to  the  internal  vol- 
ume equal  to  the  quantity  expelled ;  otherwise  the  remaining 
internal  volume  will  expand,  by  its  increased  temperature,  and 
fill  the  space  occupied  by  the  decreasing  volume,  and  thus  the 
air  becomes  more  vitiated  than  if  none  had  escaped.     The  air 
thus  brought  in  must  be  introduced  without  acting  in  a  direct 
current  upon  the  vegetable  productions  within  the  house. 

3.  The  air  thus  introduced  must  be  warmed  to  a  certain  tem- 
perature, before  it  enters  the  house.     This  temperature  should 
be  regulated  by  the  temperature  at  which  it  is  desired  to  main- 
tain the  internal  atmosphere.     If  the  desired  temperature  be 


VENTILATION   WITH   FANS.  331 

50°,  the  air  entering  should  not  be  under  that  temperature,  but 
rather  a  few  degrees  above  it. 

4.  If  the  house  be  heated  by  pipes  laid  round  the  side  of  the 
house,  the  air  thus  admitted  should  be  introduced  so  as  to  pass 
upward,  by  the  side  of  the  pipes,  on  entering  the  house.  This 
air  should  pass  regularly  and  consentaneously  upwards  ;  not  in 
sudden  blasts  and  currents,  which  have  always  an  injurious 
influence  on  the  internal  atmosphere. 

To  effect  this,  a  hot-air  chamber  should  be  placed  in  connec- 
tion with  the  heating  apparatus,  from  which  must  be  laid  air 
channels,  or  conduction  tubes,  all  around  the  house,  having 
apertures  for  the  egress  of  the  air,  at  distances  of  six  or  eight  feet 
apart.  Within  this  chamber  a  fan  might  be  used  for  drawing 
in  the  external  air  and  driving  in  the  warmed  air  through  the 
tube.  This  fan  might  be  driven  by  a  small  windmill  con- 
structed for  the  purpose. 

When  air  is  under  the  control  of  a  moving  power,  it  will  take 
any  direction  that  is  desired.  It  will  move  horizontally,  or  ver- 
tically, either  upwards  or  downwards,  and  even  in  both  direc- 
tions, at  the  same  time. 

It  is  essential,  however,  that  the  supply  to  be  warmed  should 
be  drawn  from  the  external  atmosphere ;  and  here  the  fan  may 
be  used  to  great  advantage.  In  no  case  should  the  supply  of  air 
be  drawn  from  the  interior  of  the  house.  The  vitiated  air,  as  it 
passes  upward,  should  be  allowed  to  pass  off  freely  into  the 
atmosphere. 

In  this  country,  however,  the  fan  cannot  be  so  advantageously 
applied  in  the  ventilation  of  horticultural  buildings,  as  in  north- 
ern Europe,  and  only  at  night,  the  period  when  ventilation  is 
most  needful.  The  large  amount  of  artificial  heat  necessary  in 
our  New  England  climate,  in  severe  nights,  is  more  injurious  to 
green-house  plants  than  the  excessive  heat  of  summer.  There 
is  no  impossibility,  however,  in  producing  a  constant  and  equa- 
ble motion  in  the  atmosphere  of  green-houses,  at  night ;  and 
this  may  be  effected  by  the  means  which  we  have  just  ex- 
plained. 

Fans  may  also  be  beneficially  employed  in  producing  a  cool- 
ing effect  in  the  air  at  the  top  of  the  house.  The  injurious 


332  VENTILATION    WITH    FANS. 

effect  of  the  highly-heated  air  in  the  upper  regions  must  be 
obvious.  We  have  measured  the  temperature  of  a  house  45 
feet  in  height,  and  have  found  the  temperature  at  the  floor  of  the 
house  to  be  38°,  while  the  temperature  of  the  upper  stratum  was 
103°,  showing  a  difference  of  65°.  In  many  other  cases,  we 
have  found  the  temperature  of  the  upper  stratum  of  air  in  a 
house,  above  120°,  while  the  water  cistern,  at  the  floor  of  the 
house  was  covered  with  ice.  The  application  of  a  fan  may  be 
beneficial  in  reducing  this  temperature,  and  expelling  the  foul 
air  collected  in  the  upper  portions,  at  apertures  lower  down  the 
house. 

Various  other  mechanical  contrivances,  besides  the  fan,  have 
been  used  for  producing  motion  in  the  atmosphere  of  houses. 
Among  these  may  be  mentioned  common  windmills,  of  which 
we  have  already  spoken.  The  windmill  ventilator  is  a  very 
adaptable  machine,  and  may  be  constructed  very  simply,  in  con- 
nection with  a  hot-house,  and  applied  in  moving  the  atmosphere 
of  the  house,  or  in  propelling  the  warmed  air  through  the  con- 
duction tubes  with  greater  velocity  than  it  would  acquire  by  its 
own  specific  gravity.  The  windmill,  of  course,  is  turned  by 
the  force  of  the  wind  outside  the  house,  and  is  entirely  depend- 
ent upon  the  motion  of  the  external  air,  for  the  power  it  exer- 
cises over  the  internal  atmosphere.  In  hot-houses,  with  dome- 
shaped  roofs,  it  is  well  adapted  for  drawing  off  the  highly- 
heated  air  at  the  top  of  the  house,  and  may  be  made  something 
like  the  screw  propeller  of  the  steamboats,  and  situated  directly 
in  the  apex  of  the  roof. 

Pumps  have  also  been  used  for  drawing  off  the  foul  air  from 
buildings,  although  we  are  not  aware  that  they  have  ever  been 
employed  for  ventilating  hot-houses,  for  which  they  are  not  at 
all  adapted. 

Chimney  shafts  are  well  adapted  for  producing  motion  in  the 
air,  by  the  draughts.  None  of  these  methods,  however,  are  so 
useful  as  the  fan,  when  mechanical  means  are  to  be  applied ; 
though,  for  the  practical  purposes  of  ventilation,  in  horticultural 
structures,  the  common  process  of  spontaneous  ventilation  must, 
in  general  cases,  suffice ;  — and,  therefore,  the  question  is,  as  to 
the  means  of  admitting  the  air,  and  the  temperature  at  which  it 


VENTILATION   WITH   FANS.  333 

is  to  be  admitted.  The  movements  of  the  atmosphere,  caused 
by  the  difference  of  temperature  between  the  external  and  inter- 
nal volumes,  have  been  already  considered ;  and  we  now  leave 
the  subject  to  the  consideration  of  those  who  are  engaged  in  the 
•practical  operations  of  exotic  horticulture. 


APPENDIX 


TABLE  I. 


TABLE  of  the  Expansive  Force  of  Steam,  in  Atmospheres,  and  in  Ibs. 
per  square  inch  ;  for  temperatures  above  212°  of  Fahrenheit. 

N.  B.  The  steam  is  supposed  to  be  in  contact  with  the  water  from  which  it  is  formed, 
and  the  water  and  steam  to  be  alike  in  temperature. 


DO 

Pressure. 

g  . 

Pressure. 

S  • 

Pressure. 

1! 

m 

!'! 

w 

gjj 

tri 

£§ 

2 

£ 

o  S 

E 

flj 

"•  a 

f 

Ibs. 

C  A 

S 

Ibs. 

c  J3 

•"  a 

i 

Ibs. 

jfi 

| 

fl 

1 

|5 

I 

212 
251 

1 

2 

15 
30 

431 
436 

23 
24 

345 
360 

646 
655 

150 
160 

2250 
2400 

275 

3 

45 

439 

25 

375 

663 

170 

2550 

294 

4 

60 

457 

30 

450 

671 

180 

2700 

308 

5 

75 

473 

35 

525 

679 

190 

2850 

320 

6 

90 

487 

40 

600 

686 

200 

3000 

332 

7 

105 

499 

45 

675 

694 

210 

3150 

342 

8 

120 

511 

50 

750 

700 

220 

3300 

351 

9 

135 

521 

55 

825 

707 

230 

3450 

359 

10 

150 

531 

60 

900 

713 

240 

3600 

367 

11 

165 

540 

65 

975 

719 

250 

3750 

374 

12 

180 

549 

70 

1050 

726 

260 

3900 

381 

13 

1^5 

557 

75 

1125 

731 

270 

4050 

387 

14 

?10 

565 

80 

1200 

737 

280 

4200 

393 

15 

Vk>5 

572 

85 

1275 

742 

290 

4350 

399 

16 

^40 

579 

90 

1350 

748 

300 

4500 

404 

17 

255 

586 

95 

1425 

753 

310 

4650 

409 

18 

270 

592 

100 

1500 

758 

320 

4800 

414 

19 

285 

605 

110 

1650 

763 

330 

4950 

418 

20 

300 

616 

120 

1800 

768 

340 

5100 

423 

21 

315 

627 

130 

1950 

772 

350 

5250 

427 

22 

330 

636 

140 

2100 

***  The   above  Table   is  deduced    from  the  experiments  of  MM. 
Dulong  and  Arago.     Their  calculations  extend  only  as  far  as  50  atmos- 
29 


336 


APPENDIX. 


pheres  ;   from  thence  the  pressures  are  now  calculated  to  350  atmos- 
pheres by  their  formula,  viz.  :  — 


•7153 

where  e  represents  the  pressure  in  atmospheres,  and  t  the  temperature 
above  100°  of  Centigrade.  In  this  equation  each  100°  of  Centigrade  is 
represented  by  unity. 

In  reducing  these  temperatures  from  Centigrade  to  Fahrenheit's  scale, 
vhere  the  fractions  amount  to  -5,  they  have  been  taken  as  the  next 
legree  above,  and  all  fractions  below  -5  have  been  rejected. 


TABLE   II. 


TABLE  of  the  quantity  of  Vapor  contained  in  Atmospheric  Air, 
different  Temperatures,  when  saturated. 


at 


_o 

o 

t* 

c 

1- 

*: 

1- 

o 

£ 

y 

<J 

£ 

al 

£ 

SJ 

I 

11 

2 

a 

is 

o  c 

a 

gl 

°.s 

I 

'i  s 

1 

c  o 

i 

1* 

o- 

20° 

1-52 

48° 

3-98 

76° 

9-53 

22 

1-64 

50 

4-24 

78 

10-16 

24 

1-76 

52 

4-52 

80 

10-78 

26 

1-90 

54 

4-82 

82 

11-49 

28 

2-03 

56 

5-13 

84 

12-20 

30 

2-25 

58 

5-51 

86 

12-91 

32 

2-32 

60 

5-83 

88 

13-61 

34 

2-48 

62 

6-21 

90 

14-42 

36 

2-64 

64 

6-60 

92 

15-22 

38 

2-82 

66 

7-00 

94 

16-11 

40 

3-02 

68 

7-43 

96 

17-11 

42 

3-24 

70 

7-90 

98 

18-20 

44 

3-48 

72 

8-40 

100 

19-39 

46 

3-73 

74 

8-95 

***  The  above  Table  is  computed  from  Dr.  Dalton's  Experiments  on 
the  Elastic  Force  of  Vapor. 


APPENDIX. 


337 


! 


TABLE  III. 


TABLE  of  the  Expansion  of  Air  and  other  Gases  by  Heat,  when  per- 
fectly free  from  Vapor. 


Temperature 
Fahrenheit's 
Scale. 

Expansion. 

Temperature 
Fahrenheit's 
Scale. 

Expansion. 

32° 

1000 

100° 

1152 

35 

1007 

110 

1178 

40 

1021 

120 

1194 

45 

1032 

130 

1215 

50 

1043 

140 

1235 

55 

1055 

150 

1255 

60 

1066 

160 

1275 

65 

1077 

170 

1295 

70 

1089 

180 

1315 

75 

1099 

190 

1334 

80 

1110 

200 

1354 

85 

1121 

210 

1372 

90 

1132 

212 

1376 

95 

1142 

*#*  The  above  numbers  are  obtained  from  Dr.  Dalton's  experiments, 
which  give  an  average  of  5^3  part,  or  -00207  for  the  expansion  by  each 
degree  of  Fahrenheit.  Gay  Lussac  found  it  to  be  equal  to  -£%-$  part,  or 
•002083  for  each  degree  of  Fahrenheit ;  and  that  the  same  law  extends 
to  condensable  vapors  when  excluded  from  contact  of  the  liquids  which 
produce  them. 


338 


APPENDIX. 


TABLE  IV. 

TABLE  of  the  Specific  Gravity  and  Expansion  of  Water  at  different 
Temperatures. 


Temperature,  Fah- 
renheit's Scale. 

Expansion. 

Specific 
Gravity. 

Weight 
of 
1  Cubic 
Inch, 
ingrains. 

Temperature,  Fah- 
renheit's Scale. 

Expansion. 

Specific 
Gravity. 

Weight 
of 
1  Cubic 
Inch, 
ingrains. 

30° 

•00017 

•9998 

252-714 

121° 

•01236 

•9878 

249-677 

32 

•00010 

•9999 

252-734 

124 

•01319 

•9870 

249-473 

34 

•00005 

•9999 

252-745 

127 

•01403 

•9861 

249-265 

36 

•00004 

•9999 

252-753 

130 

•01490 

•9853 

249-053 

38 

•000002    -9999 

252-758 

133 

•01578 

•9844 

248-836 

39 

•00000     1-0000 

252-759 

136 

•01668 

•9836 

248615 

43 

•00003 

•9999 

252-750 

139 

•01760 

•9827 

248-391 

46 

•00010 

•9999 

252-734 

142 

•01853 

•9818 

248-163 

49 

•00021 

•9997 

252-704 

145 

•01947 

•9809 

247-931 

52 

•00036 

•9996 

252-667 

148 

•02043 

•9799 

247-697 

55 

•00054 

•9994 

252-621 

151 

•02141 

•9790 

247-459 

58 

•00076 

•9992 

252-566 

154 

•02240 

•9780 

247-219 

61 

•00101 

•9989 

252-502 

157 

-02340 

•9771 

246-976 

64 

•00130 

•9986 

252-429 

160 

•02441 

•9760 

246-707 

67 

•00163 

•9983 

252-349 

163 

•02543 

•9751 

246-483 

70 

•00198 

•9981 

252-285 

166 

•02647 

•9741 

246-233 

73 

•00237 

•9976 

252-162 

169 

•02751 

•9731 

245-982 

76 

•00278 

•9972 

252-058 

172 

•02856 

•9721 

245-729 

79 

•00323 

•9967 

251-945 

175      -02962 

•9711 

245-474 

82 

•00371 

•9963 

251-825 

178 

•03068 

•9701 

245-218 

85 

•00422 

•9958    251-698 

181 

•03176 

•9691 

244-962 

88 

•00476 

•9952 

251-564 

184      -03284 

•9681 

244-704 

91 

•00533 

•9947 

251-422 

187     -03392 

•9671 

244-446 

94 

•00592 

•9941 

251-275 

190     -03501 

•9660 

244-187 

97 

•00654 

•9935 

251-121 

193 

•03610     -9650 

243-928 

100 

•00718 

•9928 

250-960 

196 

•03720     -9640 

243-669 

103 

•00785 

•9922 

250-794 

199 

•03829 

•9630 

243-410 

106 

•00855 

•9915 

250-621 

202 

•03939 

•9619 

243-151 

109 

•00927 

•9908 

250-443 

205 

•04049 

•9609 

242-893 

112 

•01001 

•9901 

250-259 

208 

•04159 

•9599 

242-635 

115 

•01077 

•9893  j  250-070 

212 

•04306 

•9585 

242-293 

118 

•01156 

•9885  I  249-876 

***  In  the  above  Table  the  expansions  are  calculated  by  Dr.  Young's 
formula,  22  /2  (1  —  -002/)  in  ten  millionths.  The  diminution  of  specific 
gravity  is  calculated  by  this  equation:  -0000022/2  — -00000000472/3. 
In  both  equations,  /  represents  the  number  of  degrees  above  or  below 
39°  of  Fahrenheit.  The  absolute  height  of  a  cubic  inch  of  water,  at 
any  temperature,  may  be  found  by  multiplying  the  weight  of  a  cubic 
inch  at  39°,  by  the  specific  gravity  at  the  required  temperature. 


APPENDIX. 


TABLE  V. 


339 


TABLE  of  the  Specific  Heat,  Specific  Gravity,  and  Expansion  by  Heat, 

of  different  Bodies. 
Barometer  30  Inches.  —  Thermometer  6QO. 


Specific  Heat. 

Specific 
gravity 

Weight  of 
100  Cubic 
Inches. 

Linear  Ex- 
pansion by 
1800  of  heat, 
from 
320  to  2120. 

Of  equal  Weights, 
by 
Berard  and  Delaroche. 

IOf  equal  Volumes, 
by 
Petit  and  Dulong. 

Barometer  30  Inches. 
Thermometer  6Qo. 

Air  (atmospheric)  .... 
—  (dry)  .                  Avihon 

•2669 
•2767 
•8470 
•2754 
•2369 
•2210 
•2884 
3-2936 
•4207 
•2361 
1-000 

1-000 
•0288 

•1498 
•0949 

•0298 

•1100 
•0293 
•1035 

•0314 
•0557 

1-000 

'•633 
•9722 
1-5277 
1.5277 
•9722 
•0694 
•9722 
Mill 

Grains. 
30-519 

19-  321* 
29-65 
46-596 
46-596 
29-65 
2-118 
29-65 
33-888 

•00186671 
•00193000 

•00172244 
00146606 
00081166 
00087572 
00111111 
00122045 
00284836 

00228300 
00099180 
00208260 
00250800 
00205800 
00107875 
00136900 

00217298 
00294200 

Aqueous  vapor  ... 

Azote    

oxide  of  

Carbonic  acid      

—  -  —  oxide  

Hydrogen     

Oxygen 

Water 

Water  

1-000 

9-880 
7-824 
8-396 
8-600 
8-900 
19-250 
2-760 
2-520 
7-248 
7-788 
11-350 
8-279 

21-470 
10-470 

Ounces. 
57-87 
571-7 
452-77 
485-87 
497-6 
515-0 
1114-0 
159-72 
145-83 
418-9 
450-2 
656-8 
478-5 

1242-4 
605-8 

453-7 
452-31 
115-1 
353-5 
421-9 
416-0 

Brass    

Cobalt  

Gold  

Glass  (flint)     

(tube) 

Iron  (cast)  
(bar)   . 

Lead     

Nickel  

Pewter  (fine)  .... 

Silver   

Solder  (lead  2  -f-  tin  1)     . 

Spelter  (brass  2-j-zinc  1) 
Steel  (untempered)    .   .    . 
(yellow  tempered)    . 

;; 

•1880 
0912 
0514 
0927 

7-'840 
7-816 
1-990 
6-115 
7-291 
7-191 

Tin    . 

Zinc  

*#*  Air  is  taken  as  the  standard  for  the  specific  gravity  of  the  gases, 
and  water  as  the  standard  for  the  solids. 
*  Specific  gravity  of  steam  at  212°  =—481.  Weight  of  100  cubic  inches.  14-680  grains. 

29* 


340 


APPENDIX. 


TABLE  VI. 


TABLE  of  the  Effects  of  Heat. 


Greatest  heat  observed 

Hessian  crucible  fused 

Cast  iron  thoroughly  melted 

Greatest  heat  of  a  smith's  forge  .... 
"  "  of  a  plate-glass  furnace  .  . 
"  "  of  a  flint-glass  ditto  .  .  . 

Derby  porcelain  vitrifies 

Welding  heat  of  iron  (greatest)     .... 

"         "      "    "      (least) 

Fine  gold  melts 

Fine  silver  melts 

Swedish  copper  melts 

Brass  melts 

Diamond  burns      

Red  heat  fully  visible  in  daylight      .   .   . 

Iron  red-hot  in  the  twilight 

Charcoal  burns 

Heat  of  a  common  fire 

Iron  bright-red  in  the  dark      

Zinc  melts  (680°  Davy) 

Mercury  boils  (Black  600°)  (Secondat  644°)  Petit  and 

Dulong) 

"          "      (Crichton  655°)  (Irvine  672°)  (Dalton)  .    . 
Lowest  ignition  of  iron  in  the  dark    .    .    . 
Lead  melts  (Guy ton  and  Irvine  594°)  (Crichton)  .    . 
Steel  becomes  dark  blue,  verging  on  black 

«        "          a  full  blue 

Sulphur  burns 

Steel  becomes  a  bright  blue 

purple 

u        "          brown,  with  purple  spots    . 

"         "          brown 

Bismuth  melts   .    .   '. 

Steel  becomes  a  full  yellow 

"         "          a  pale  straw  color    .... 

Tin  melts 

Steel  becomes  a  very  faint  yellow  .  .  . 
Tin  3  -f-  lead  2  -j-  bismuth  1,  melts  .  .  . 
Tin  and  bismuth,  equal  parts,  melts  .  . 
Bismuth  5-j-tin  3 -j- lead  2,  melts  .  .  . 

"Water  boils  (barometer  30  in.) 

Water  freezes 

Milk  freezes 

Vinegar  freezes 

Sea  water  freezes 

Strong  wine  freezes  .    .    • 

Quicksilver  congeals 

Sulphuric  aether  congeals 

Natural  temperature  at  Hudson's  Bay 
Great  artificial  cold       


Wedgwood's 
Scale. 

Fahrenheit's 
Scale. 

185 
150 
150 
125 
124 
114 
112 
95 
90 
32 
28 
27 
21 
14 
1 

25127 
20557 
20577 
17327 
17197 
15897 
15637 
13427 
12777 
5237 
4717 
4587 
3807 
2897 
1077 
884 

802 

790 

752 

700 

etit  and 

656 

alton)  .  . 

660 
635 

o  .  .  .  . 

612 
600 

560 

560 

550 

530 

510 

490 

476 

470 

450 

442 

430 

334 

283 

212 

212 

32 

30 

28 

28 

20 

—39 

—47 

51 

—91 

APPENDIX. 


341 


TABLE  VII. 

TABLE  of  the  Quantity  of  Water  contained  in  100  feet  of  Pipe  of  dif- 
ferent diameters. 


Diameter 
of  Pipe. 

Contents  of  100  Feet 
in  length. 

Inches. 

Gallons. 

h 

•84 

1 

3-39 

y 

7-64 

2 

13-58 

2i 

21-22 

3 

30-56 

4 

54-33 

5 

84-90 

6 

122-26 

TABLE  VIH. 

TABLE,  showing  the  Effects  of  Wind  in  Cooling  Glass. 


Time  of  cooling  the  Thermometer  20°,  from  120°  to  100°, 

Velocity 

Fahrenheit. 

of  the 

wind 
in  miles 
per  hour. 

Observed 
time  of 
cooling. 

Time  re- 
duced to 
decimals 
of  a 

Corrected  time,  being  the  inverse  of  the  square 
root  of  the  velocities,  in  decimals  of  a  minute. 

minute. 

3-26 

2'  35" 

2-58 

2-58 

5-18 

2  10 

2-16 

2-04 

6-54 

1  55 

1-91 

1-82 

8-86 

1  40 

1-66 

1-56 

10-90 

1  30 

1-50 

1-41 

13-36 

1  15 

1-25 

1-27 

17-97 

1    5 

1-08 

MO 

20-45 

1    0 

1-00 

1-03 

24-54 

0  55 

•91 

•94 

27-27 

0  48 

•81 

•88 

342 


APPENDIX. 


TABLE  IX. 

Experiments  on  the  Cooling  Effect  of  Windows.* 

These  experiments  were  made  in  a  wooden  house,  double  plastered, 
with  a  space  between  the  two  plasterings  ;  walls  6  inches  thick.  Heat 
introduced  from  a  hot-air  furnace,  heated  air  being  shut  off  when  the 
room  was  heated  to  a  proper  temperature.  Thermometer  four  feet  from 
the  floor.  When  the  windows  were  closed,  two  thicknesses  of  blankets 
were  fastened  closely  to  the  window-frame  internally. 

Three  windows,  equal  to  33-21  square  feet  ;  walls,  531  square  feet  ; 
cubic  contents  of  room,  1930  feet,  being  9  feet  high,  16-5  feet  long,  13 
feet  wide. 

The  room  was  kept  as  nearly  as  possible  under  the  same  circum- 
stances. 


External       Internal 
Thermom.    Thermom. 


March  19,  1843.    26 
25 


o 

74 
64 


22  74 

18  59 


Weather  calm,   windows 
uncovered. 


j  Windows    covered    with 
blankets. 


March  20. 


March  21. 


25 


24 
22 


24 

19 


74 

64 


74 

61 


74 
64 


74 
64 


h.    m. 
9     1 

10  15 

74 

11  41 
2     5 

144 


8  8    ( 

9  24   1  Windows  uncovered. 

76 

10  17   (  Windows    covered   with 
12  22  j  '  blankets. 


125 

8  51 

10  19 

88 

11  26 

12  16 

50 


Calm,  windows  covered. 


Windows  uncovered, 
calm. 


The  experiments  \rere  also  made  in  other  rooms,  with  wooden  shut- 
ters internally. 

The  results  are  as  follows  :  — 

1st,  room  cooled  10°  in    74'  =  1°  in  7-4',  windows  open. 
"  "        15C  in  144'  =  1°  in  9-6',  windows  closed. 

2d,  room  cooled  10°  in    76'  =  1°  in  7-6',  windows  open. 


*  Wyman  OR  Ventilation. 


APPENDIX.  343 

2d,  room  cooled  13°  in  125'  =  1°  in  9-6',  windows  closed. 
3d,  room  cooled  10°  in    88'  =  1°  in  8-8',  windows  closed. 
"  "        10°  in    507  =  1°  in  5-0',  windows  open. 

Experiment  with  wooden  shutters  :  — 
Room  cooled  10°  in  93'  =  1°  in  9-3',  shutters  closed. 
"        "       10°  in  58'  =  1°  in  5-8',  shutters  open. 

From  the  above,  the  effect  of  glass  is  very  evident,  and  also  the  advan- 
tage of  curtains  and  shutters.  We  shall  not  attempt  to  form  any  gen- 
eral rule,  since  it  could  be  applied  correctly  only  under  circumstances 
which  differed  very  little  from  the  above. 

The  preparation  for  covering  white  cotton  for  interior  windows  is 
composed  of  4  oz.  of  pulverized  dry  white  cheese,  2  oz.  of  white  slack 
lime,  and  4  oz.  of  boiled  linseed  oil.  These  three  ingredients  having 
been  mixed  with  each  other,  4  oz.  of  the  white  of  eggs,  and  as  much  of 
the  yolk,  are  added,  and  the  mixture  then  made  liquid  by  heating. 
The  oil  combines  easily  with  the  other  ingredients,  and  the  varnish  re- 
mains pliable  and  quite  transparent.  It  is  applied  with  a  brush. 


344 


APPENDIX. 


TABLE   X. 

Weights  of  "Watery  Vapor  in  one  Cubic  Foot  of  Air,  at  Dew-points  from 
0°  to  100°  Fahrenheit. 


1  Degrees 
Fahrenheit. 

1  Grains  in  a 
foot. 

1  Degrees 
Fahrenheit. 

Grains  in  a 
foot. 

l|. 

»! 

°& 

Grains  in  a 
foot. 

Degrees 
Fahrenheit.  1 

Grains  in  a 
foot. 

0 

0-186 

26 

1-915 

51 

4-382 

76 

9-523 

1 

0810 

27 

1-986 

52 

4-524 

77 

9-813 

2 

0-836 

28 

2-054 

53 

4-671 

78 

10-111 

3 

0-864 

29 

2-125 

54 

4-822 

79 

10-417 

4 

0-893 

30 

2-197 

55 

4-978 

80 

10-732 

5 

0-925 

31 

2-273 

56 

5-138 

81 

11-055 

6 

0-957 

32 

2-350 

57 

5-303 

82 

11-388 

7 

0-992 

33 

2-430 

58 

5-473 

83 

11-729 

8 

1-028 

34 

2-513 

59 

5-648 

84 

12-079 

9 

1-065 

35 

2-598 

60 

5-828 

85 

12-439 

10 

1-103 

36 

2-686 

61 

6-013 

86 

12-808 

11 

1-143 

37 

2-776 

62 

6-204 

87 

13-185 

12 

1-184 

38 

2-870 

63 

6-400 

88 

13-577 

13 

1-226 

39 

2-966 

64 

6-602 

89 

13-977 

14 

1-270 

40 

3-066 

65 

6-810 

90 

14-387 

15 

1-315 

41 

3-168 

66 

7-024 

91 

14-809 

16 

1-361 

42 

3-274 

67 

7-243 

92 

15-241 

17 

1-409 

43 

3-382 

68 

7-469 

93 

15-684 

18 

1-459 

44 

3-495 

69 

7-702 

94 

16-140 

19 

1-510 

45 

3-610 

70 

7-941 

95 

16-607 

20 

1-563 

46 

3-729 

71 

8-186 

96 

17-086 

21 

1-618 

47 

3-851 

72 

8-439 

97 

17-577 

22 

1-674 

48 

3-979 

73 

8-699 

98 

18-081 

23 

1-733 

49 

4-109 

74 

8-966 

99 

18-598 

24 

1-793 

50 

4-244 

75 

9-241 

100 

19-129 

25 

1-855 

APPENDIX. 


345 


TABLE  XI. 

Dalton's  Table  of  the  Force  of  Vapor,  from  32°  to  80°. 


Tempe- 
rature. 

Force  of  va- 
por in  iaches 
of  mercury. 

Tempe- 
rature. 

Force  of  va- 
x>r  in  inches 
of  mercury. 

Tempe- 
rature. 

Force  of  va- 
x>r  in  inches 
of  mercury. 

32° 

0-2000 

49° 

0-3483 

65 

0-6146 

33 

0-2066 

50 

0-3600 

66 

0-6355 

34 

0-2134 

51 

0-3735 

67 

0-6571 

35 

0-2204 

52 

0-3875 

68 

0-6794 

36 

0-2277 

53 

0-4020 

69 

0-7025 

37 

0-2352 

54 

0-4171 

70 

0-7260 

38 

0-2429 

55 

0-4327 

71 

0-7507 

39 

0-2509 

56 

0-4489 

72 

0-7762 

40 

0-2600 

57 

0-4657 

73 

0-8026 

41 

0-2686 

58 

0-4832 

74 

0-8299 

42 

0-2775 

59 

0-5012 

75 

0-8581 

43 

0-2866 

60 

0-5200 

76 

0-8873 

44 

0-2961 

61 

0-5377 

77 

0-9175 

45 

0-3059 

62 

0-5560 

78 

0-9487 

46 

0-3160 

63 

0-5749 

79 

0-9809 

47 

0-3264 

64 

0-5944 

80 

1-0120 

48 

0-3372 

NOTE  TO  TABLE  XII. — (See  next  page.) 

To  determine  the  dew-point,  take  two  thermometers,  the  scales  of 
which  agree,  cover  the  bulb  of  one  with  thin  muslin,  and  wet  it  with 
water ;  swing  both  thermometers  in  the  air,  that  they  may  be  exposed  under 
similar  circumstances,  and  note  the  height  of  the  mercurial  column  in 
each,  after  it  has  become  stationary.  Ascertain  the  difference  between  the 
heights  of  the  two  columns.  In  the  following  table,  find  a  number  at  the 
top  corresponding  to  the  difference  of  heights,  and  in  the  left  hand 
column  the  degree  answering  to  the  temperature  indicated  by  the  dry 
bulb  thermometer ;  the  figure  at  the  intersection  of  the  two  lines  is  the 
dew-point. 

Suppose,  for  instance,  the  dry  bulb  indicated  70°,  and  the  wet  bulb 
61° ;  70  —  61=9,  which  is  found  at  the  top  of  the  table ;  in  the  column 
beneath,  and  against  70°,  is  55°,  the  dew-point. 


346 


APPENDIX. 


TABLE  XII. 


Table  for  ascertaining  Dew-point  by 


Temp, 
of  air 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

(13 

14 

~90° 

88-7 

87-5 

86-1 

85-1 

83-8 

82-581-2 

79-9|78-e 

77-S 

751 

J7T 

473- 

71-5 

89 

87-7 

86-5 

85-3 

84-0 

82-7 

81-480- 

78-8i77-4 

76-f 

74-e 

>  73-2  71-6 

70-3 

88 

86-7 

85-5 

84-3 

83-0 

81-7 

80-479- 

77-7|76-2 

74-S 

73-£ 

•  72- 

170-b 

69-1 

87 

85- 

84-5 

83-2 

81-9 

80-6 

79-378-1 

76-675-2 

73-g 

72-4 

70-969-4 

67-9 

86 

84- 

83-5 

82-2 

80-9 

79-6 

78-276-9 

75-5,74-1 

72-7 

71-2 

69-768-2 

66-6 

85 

83- 

82-4 

81-1 

79-8 

78-5 

77-275-8 

74-4,73  0 

71-5 

70-068-567-0 

65-4 

84 

82- 

81-4 

80-1 

78-8 

77-5 

76-li74-7 

73-3,71-8 

70-4 

68-S 

67-365-" 

64-1 

83 

81- 

80-4 

79-1 

77-8 

76-4 

75-073-6 

72-0 

70-7 

69-267*7 

66-164-5 

62-8 

82 

80- 

79-4 

78-1 

76-7 

75-3 

73-9I72-5 

71-0 

69-6 

68-1 

66-564-963-2 

61-5 

81 

79-7 

78-3 

77-0 

75-6 

74-2 

72-871-4 

70-0 

68-4 

66-965-3 

63T62-0 

60-3 

~80~ 

78-6 

77-3 

76-0 

74-6 

73-2 

71-7170-3 

08-8672 

65-7|64-l  62-4  60-7 

58-9 

79 

77-6 

76-3 

75-0 

73-5 

72-1 

70-769-2 

67-666-1 

64-5  62-8  61-li59-4 

57-6 

78 

76-6 

75-3 

73-9 

72-5 

71-0 

69-5  68-0 

66-565-0 

63-3!61-6  59-858-1 

56-2 

77 

75-6 

74-2 

72-8 

71-4 

69-9 

68-4 

66-9 

65-363-7 

62-1 

60-358-556-7 

54-8 

76 

74-6 

73-2 

71-8 

70-3 

68-9 

67-3 

65-8 

64-262-5 

60-8  59-  157-2  55-3 

53-4 

75 

73-6 

72-2 

70- 

69-2 

67-7 

66-2  64-b 

63-061-3 

59-5  57-7  55-9  54-0 

52-0 

74 

72-6 

71-1 

69- 

68-2 

66-6 

65-163-4 

ul-860-1 

58-3  56-4  54-5  52-5 

50-4 

73 

71-5 

70-1 

68- 

67-1 

65-5 

64-0  62-3 

60-658-8 

57-0  55-153-1151-1 

49-0 

72 

70-5 

69-1 

67- 

66-0 

64-4 

62-8 

61-1 

59-357-5 

55-753-7 

51-7149-6 

47-3 

71 

69-5 

68-0 

66- 

64-9 

63-3 

61-6 

59-9 

58-156-2 

54-452-4 

50-348-1 

45-7 

70 

68-5 

67-0 

65- 

63-8 

62-2 

60-5 

58-7 

StHJBlFo 

530  51-0  4¥8  46-5 

44~1 

69 

67-4 

66-0 

64- 

62-7 

61-0 

59-3 

57-5 

55-6  53-7 

51-6  49-5  47-3  44-9 

42-4 

68 

66-4 

64-9 

63- 

61-6 

59-9 

58-1 

56-3 

54-352-3 

50-2  48-0  45-7!43-2 

40-5 

67 

65-4 

63-8 

62-2 

i)0-5 

58-7 

56-9 

55-0 

53-051-0 

48-8  46-5  44-1141-5 

38-8 

66 

64-4 

62-7 

61-1 

59-3 

57-5 

55-7 

53-7 

51-7 

49-6 

47-3'45-042-4i39-7 

36-8 

65 

63-3 

61-7 

60-0 

58-2 

56-4 

54-5 

52-5 

50-4 

48-2 

45-843-4 

40-7i37-9 

34-8 

64 

62-3 

60-6 

58-  " 

37-  1 

55-2 

53-2 

51-2 

49-046-7 

44-341-7 

39-0:36-0 

32-7 

63 

61-3 

59-6 

57-8 

55-8 

54-0 

520 

49-8 

47-645-1 

42-740-1 

37-1134-0 

30-5 

62 

60-3 

58-5 

30-7 

54-8 

52-8 

50-7 

48-5 

46-2  43-7 

41-138-3  35-2j31-9 

28-2 

61 

59-2 

57-4 

55-5 

53-6 

51-5 

49-4 

47-1 

41-7 

42-2 

39-4  36-4  33-2  29-7 

25-7 

60 

58-2 

56-3 

54.4 

5JF4 

50-3 

48-1 

45-7 

IJFS 

40-6 

3T734-63M 

27-3 

23-0 

59 

57-2 

55-3 

53-3 

51-2 

49-1 

46-8 

44-3 

41-739-0 

35-9  32-6  28-9  24-8 

0-1 

58 

56-1 

54-2 

52-2 

50-0 

47-8 

45-4  42-9 

40-1  37-2  34-0  30-5'26-6|22-l 

7-0 

57 

55-1 

53-1 

51-0 

18-8 

46-5 

44-041-4 

38-5  35  5  32-1  28-3  24-1U9-2 

3-5 

56 

54-0 

52-0 

49-8 

47-6 

45-2 

42-6  39-8 

36-833-6 

30-0  26-0  '21-4I16-1 

9-5 

55 

53-0 

50-8 

48-6 

16-3 

43-8 

41-138-2 

35-1 

31-8 

27-823-4 

18-4 

12-4 

4-9 

54 

51-9 

49-7 

47-5 

45-0 

42-4 

39-636-6 

33-329-7 

25-620-8 

15-3 

8-5 

-0-2 

53 

50-9 

48-6 

46-2 

43-8 

41-1 

38-134-8 

31-327-423-0 

17-8 

11-5 

3-7 

52 

49-8 

47-5 

15-1 

42-4 

39-6 

36-633-2 

29-725-320-5, 

14-8 

7-8 

-1-4 

51 

48-8 

46-4 

43-S 

41-1 

38-2 

35-031-4 

27-422-9  17-7 

11-3 

3-3 

50 

4T7 

45-2 

126 

39~7 

3lH3 

33-3:29-5 

25-320-4 

14-7 

7-4 

-2-0 

49 

46-6 

44-1 

41-3 

38-4 

35-1 

31-627-5 

23-0 

17-7 

11-2 

2-9 

48 

45-5 

42-9 

40-0 

37-0 

33-5 

29-7)25-5 

20-614-7 

7-3 

-2-4 

47 

44-4 

41-7 

38-7 

35-5 

31-9 

27-9J23-3 

7-9 

11-4 

3-1 

46 

13-4 

40-5 

37-4 

34-0 

30-1 

25-7 

20-8 

4-8 

7-4 

-2-6 

45 

12-2 

39-3 

36-1 

32-5 

28-4 

23-9 

18-5 

2-0 

3-6 

44 

il'l 

38-1 

34-7 

30-9 

26-2 

21-7 

15-8 

8-5 

-1-2 

43 

40-1 

36-8 

33-2 

29-3 

24-7 

19-4 

129 

4-6 

-7-0 

42 

38-9 

35-6 

31-8 

27-6 

22-7 

16-9 

9-7 

0-2 

41 

37-8 

34-3 

30  3 

25-8 

20-b 

14-3 

6-2 

-5-0 

40 

36-7 

33-0 

28-8 

23-9 

18-1 

11-4 

2-2 

APPENDIX. 


347 


TABLE    XII.  —  Continued. 
Observations  on  the  Wet  and  Dry  Bulb  Thermometer. 


Temp, 
of  air. 

~9(F 

15 
TtM) 

16 
681 

17 
66^8 

18 
6T2 

19 
6T6 

1  20    21 
(JHJifiO7! 

22 

sFs 

23 
56:4 

24  1  25  1  26     27 
5TI  52  4  50  3i4870 

28 
4F6 

89 

68-8 

67-2 

65-6 

63-9 

62-2 

60-558-7 

56-9 

54-9  52-9  50-8  48-5146-2 

88 

67-5 

65-9 

64-3 

6£-6|60-9 

59-157-2 

55-3 

53-3,51-2  49-0  46-7J44-3 

87 
86 

66-3 
65-0 

64-7 
63-3 

63-0 
61-6 

61-3 
59-9 

59-5 
58-1 

57-7:55-8 
56-2:54-2 

l53-g 
52-2 

51-7  49-6  47-3  44-9 
50-1  47-8  45-5  43-0 

42-4 

85 

63-7 

62-0 

60-3 

58-5 

56-6 

54-7:52-7 

50-6 

48-446-1 

43-641-0 

84 

62-4 

60-7 

59-0 

57-1 

552 

53-2;5l-l 

48-9 

46-644-2 

41-638-9 

83 

61-1 

59-4 

57-5 

55-6 

53-7 

51-649-5 

47-2 

44-8,42.339-6 

82 

59-8 

58-0 

56-1 

54-2 

52-1 

50-047-8 

45-4 

43-040-337-4 

81 

58-5 

56-6 

54-7 

52-7 

50-6 

48-446-1 

43-6 

41-038-2 

35-2 

80 

5T7! 

55^2 

53^2 

5FI 

49-0 

4677  4F3 

IP? 

39-0;36-0 

79 

55-7 

53-7 

51-7 

49-6 

47-3 

45-042-4 

39-7 

36-833-7 

78 

54-2 

52-2 

50-1 

180 

45-6 

43-1 

40-4 

37-6 

34-6 

31-2 

77 

52-8 

50-7 

485 

46-2 

43-8 

41-238-4 

35-4 

32-2 

76 

51-3 

49-2 

46-9 

44-5 

42-0 

39-2 

36-3 

33-1 

29-7 

75 

49-8 

47-6 

45-2 

42-7 

40-1 

37-2 

34-1 

30-7 

27-0 

74 

48-2 

46-0 

43-5 

40-8 

38-1135-0 

31-7 

28-1 

73  146-6 

44-2 

41-6 

39-0 

36-OJ32-829-2 

25-3 

72 

45-0 

42-5 

39-8 

36-9 

33-8 

30-4 

26-5 

22-3 

71    43-3 

40-6 

37-8 

34-8 

31-4 

27-8 

237 

~TQ~ 

41-5 

SS7? 

35^8 

321) 

2<F6 

251J20K5 

69    39-7 

36-8 

33-6 

30-2 

26-3 

22-0117-1 

68  |37-8 

34-7 

31-4 

27-7 

23-5 

18-8 

67 

35-8 

32-5 

29-0 

25-0 

20-4 

15-1 

66 

33-7 

30-2 

26-4 

22-1 

17-0 

65  J31-5 

27-8 

23-6 

18-8 

13-2 

64 

29-2 

25-2 

20-6 

15-3 

63 

27-6 

22-3 

17-3 

11-4 

62 

24-0 

19-3 

13-7 

61 

21-2 

15-9 

9-6 

60 

187! 

12-2 

59  |l4-6 

7-9 

58 

10-8 

57 

6-4 

30 


348 


APPENDIX. 


Air. 


J.  *  1. 

.s?  s  « 

*!* 


S  i  1 

i    1    3 

:    .   . 

o.>»5 

lil 


<->      -^3     «-> 

11  c     l 

•«-» 

i 


-5;tic2t:"§-' 


S- 

H     <^ 


.-. 


§    -§c 

0     OK 


•<      -U 


o    o     p      T« 

O  lO     T*<        •**!        ^H 


TABLE 

A  Table  of  the  Anal 


!•»* 


^*        "^ 

o      4 


O        ^-^COO 

us      <N.-H&o 


OpOp        O        ~ 


cocoo<N 


S     ^H        CD 


«prf     ^H 


0     ^i 


S    S 


'HS=)3Sc 


sli          I 


££R 

- 


llfi 

i 


|?a 


£  1 

t? 
II 

•«* 


. 

^    1  13  s 


V    >    V 


I  u 


APPENDIX, 


349 


TABLE  XIV. 

Constitution  of  the  Atmosphere. 

Dumas  and  Boussingault  analyzed  atmospheric  air  by  fixing  its  oxygen 
on  copper,  which  was  weighed  j  the  azote  was  also  collected  and 
weighed. 

1000  parts  of  air  at  Paris  contained  by  weight :  — 

Oxygen.  Azote. 

April  27,  fair  weather, 229.2  770-8 

"     "       "         "          229.2  770.8 

"    28,     "        "          230.3  769.7 

«     "       "         "          230.9  769.1 

"    29,     "        "          230.3  769.7 

"     "       "         "          230.4  769.6 

May  29,  rainy, 230.1  769.9 

July  20,  mid-day,  rainy, 230.5  769.5 

"      21,  midnight,  clear, 230.0  770.0 

"      26,  mid-day,  clear, *  *  .  *  .  230.7  769.3 

769.8 
792=1000 


Consumption  of  Oxygen  and  Formation  of  Carbonic  Acid. 

From  experiments  of  Dumas  on  himself,  it  appears  that  about  twenty 
cubic  inches  were  received  into  the  lungs  at  each  inspiration,  and  from 
Hfteen  to  seventeen  inspirations  per  minute.  The  expired  air  contained 
from  three  to  four  per  cent,  of  carbonic  acid,  and  had  lost  from  four  to 
six  per  cent,  of  oxygen.  These  data,  for  each  day  of  twenty-four  hours, 
give, 

16  insp.  X  20  cubic  inches  =  320  cubic  inches  expired  per  minute. 

19,200    "          "          "  hour. 

460,800    "          "          "  day 


350 


APPENDIX. 


TABLE  XV. 

A  Table  of  Mean  Temperatures  of  the  hottest  and  coldest  months. 


Mean' 

Pemp.  of 

Latitude. 

Longitude. 

est 
Month. 

Coldest 
Month. 

Authorities. 

St.  Petersburgh, 

59  56  N. 

30  19  E. 

65-660 

8-600 

Humboldt. 

Moscow, 

55  45  N. 

37  32  E. 

70-52 

608 

" 

Melville  Island,  \ 

74  47  N. 

110  48  W 

39-08 
42-41 

-35-52 
-32-19 

Hugh  Murray. 
Ed.  Phil.  Journal. 

Copenhagen, 
Edinburgh, 

55  41  N. 

55  57  N. 

12  35  E. 
3  10W. 

65-66 
59-36 

27-14 
38-30 

Humboldt. 

Geneva, 

46  12  N. 

6    8E. 

66-56 

34-16 

it 

Vienna, 

48  12  N. 

16  22  E. 

70-52 

2660 

M 

Paris, 

48  50  N. 

2  20  E. 

65-30 

36-14 

H 

London, 
Philadelphia, 

51  SON. 
39  56  N. 

0    5  W. 
75  16  W. 

64-40 
77-00 

37-76 
32-72 

! 

New  York, 

40  40  N. 

73  58  W. 

80-70 

25-34 

« 

Pekin, 

39  54  N. 

116  27  E. 

84-38 

24-62 

1 

Milan, 

45  28  N. 

9  11  E. 

7466 

36-14 

( 

Bordeaux, 

44  50  N. 

0  34  W. 

73-04 

41-00 

1 

Marseilles, 

43  17  N. 

5  22  E. 

74  '66 

44-42 

( 

Rome, 

41  53  N. 

12  27  E. 

77-00 

42-26 

1 

Funchal, 

32  37  N. 

16  56  W. 

75-56 

64-04 

1 

Algiers, 

36  48  N. 

3    1  E. 

82-76 

6XHH 

' 

Cairo, 

30    2  N. 

30  18  E. 

85-82 

56-12 

Vera  Cruz, 

19  11  N. 

96     1  W. 

81-86 

71-06 

1 

Havanna, 

23  10  N. 

82  13  W. 

83-84 

69-98 

' 

Cumana, 

10  27  N. 

65  15  W. 

84-38 

79-16 

(( 

Canton, 

23  10  N. 

113  13  E. 

84-50 

57-00 

Anglo-Chinese  Calendar. 

Macao, 

22  10  N. 

113  32  E. 

86-00 

63-50? 

«            it           « 

Canaries, 

23  30  N. 

16  00  W. 

78-90 

63-70 

Brande's  Journal. 

Lohooghat  (5800  ) 
feet  above  the  > 
sea,)                   ) 

29  23  N. 

79  56  E. 

6934 

43-57 

$  Trans.    Med.    Phya.    Soc. 
?         Calc. 

Fattehpur, 
Gurrah  Warrah, 

25  56  N. 
23  ION. 

80  45  E. 
79  54  E. 

74-94 

87-45 

58-74 
60-23 

Gleanings  in  Science. 

Calcutta,              \ 

22  40  N. 

88  25  E. 

85-70 
86-86 

66.20 
70-10 

Journal  As.  Soc. 

Ava, 

21  51  N. 

95  98  E. 

88-15 

64-12 

Gleanings  in  Science. 

Bareilly, 

28  23  N. 

79  23  E. 

91-91 

5650 

ti         n         « 

Chunar, 

25    9  N. 

82  54  E. 

90-00 

58-00 

Ed.  Ph.  Journ. 

Cape     of    Good  ) 

Hope      (Feld-  [ 

34  23  S. 

18  25  E. 

74-27 

57-43 

Herschel  (MSS.) 

hausen.)            ) 

Bahamas, 

26  SON. 

78  30  W. 

83-52 

6907 

Hon.  J.  C.  Lees  (MSS.) 

Swan  River, 
Bermuda, 

32  00  S. 
32  15  N. 

115  50  E. 
64  SOW. 

78-00 
76-75 

54-84 
57-90 

Milligan. 
Col.  Emmett. 

APPENDIX. 


361 


TABLE  XVI. 

The  following  proportions  between  the  Mean  Temperature  of  the  earth, 
as  indicated  by  springs,  and  that  of  the  atmosphere,  have  been  collected 
from  various  sources. 


Names  of  Places. 

Authority. 

Temp, 
of 

Earth. 

Mean 
Temp,  of 
Atmos- 
phere. 

Berlin,  

Wahlenberg,    .   .   . 

49-28° 

46-40° 

u 

47-30 

42-03 

Upsal, 

ii 

43-70 

42-08 

Paris,     

(Catacombs,)  ... 

53-00 

51-00 

Charleston,       ...... 

63-00 

68-00 

u 

53-00 

53-42 

Virginia           •   • 

(i 

57-00 

57-00 

Dewev. 

47-21 

44-73 

Volney,     

44-00 

56-00 

Raith  (Scotland,)  

Ferguson,     .... 

47-70 

47-00 

Watson,    

52-46 

51-42 

Kendal          (do  ) 

n 

47-20 

47-04 

Keswick,      (do.)    

tt 

46-60 

48-00 

Leith,  (Scotland,)  

47-30 

48-36 

South  of  England,  

Rees'  Cyclo,     .   .   . 

48-00 

50-62 

Torrid  Zone,    

63-00 

81-50 

30* 


352 


APPENDIX. 


TABLE  XVII. 


Showing  the  Specific  Gravity  of  different  kinds  of  timber. 

I.  H. 

Box, _  942 

Plum-tree, —  872 

Hawthorn, —  871 

Beech, 852  

Ash, 845  670 

Yew,      807  744 

Elm, 800  568 

Birch, 738 

Apple, 733  734 

Pear,      732 

Yoke-elm, 728 

Orange-tree, 705 

Walnut-tree, 660 

Pine,     657  763 

Maple, 645 

Linden-tree, 604  559 

Cypress, 598  

Cedar, 561 

Horse  chestnut, 551 

Alder, 538 

White  poplar, 529 

Common  poplar,      383  387 

Cork, 240  

*#*  The  column  I.,  in  the  above  table,  exhibits  the  specific  gravity 

of  different  woods,  adopted  by  the  Annuaire  du  Bureau  des  Longitudes. 

The  second  column  contains  the  results  obtained  by  M.  Karmarsch. 


APPENDIX. 


363 


TABLE    XVIII. 

Solutions  for  the  impregnation  of  wood  which  is  exposed  to  the  atmos- 
phere, for  the  purpose  of  preserving  it  from  decay. 


Tar. 

Sulphate  of  Copper. 

Sulphate  of  Zinc. 

Sulphate  of  Iron. 

Sulphate  of  Lime. 

Sulphate  of  Magnesia. 

Sulphate  of  Barytes. 

Sulphate  of  Soda. 

Alum. 

Carbonate  of  Soda. 

Carbonate  of  Potash. 

Carbonate  of  Barytes. 

Sulphuric  Acid. 

Acid  of  Tar,  (pyroligneous  acid.) 

Common  Salt. 

Vegetable  Oils. 

Animal  Oils. 

Coal  Oil,  (Naphtha,) 

Resins. 

Quick-lime. 


Glue. 

Corrosive  sublimate.* 

Nitrate  of  Potash. 

Arsenical  Pyrites  water,  —  (water 
containing  arsenical  acid.) 

Peat  Moss,  (containing  tannin.) 

Creosote  and  Eupion. 

Crude  Acetate,  or  pyrolignite  of  iron. 

Peroxide  of  Tin. 

Oxide  of  Copper. 

Nitrate  of  Copper. 

Acetate  of  Copper. 

Solution  of  Bitumen,  in  oil  of  tur- 
pentine. 

Yellow  Cromate  of  Potash. 

Refuse  Lime-water  of  Gas-works. 

Caoutchouc,  dissolved  in  naptha. 

Drying  Oil. 

Beeswax,  dissolved  in  turpentine. 

I  Chloride  of  Zinc. 


*  Corrosive  sublimate  is  one  of  the  most  efficient  of  all  these  antiseptic  applications. 
It  was  proposed  by  Mr.  Kyan  as  a  preventive  of  dry  rot,  under  the  idea  of  its  acting 
as  a  poison  to  the  fungi  and  insects,  which  were  the  supposed  cause  of  the  disease. 
But  thia  explanation  of  the  action  of  corrosive  sublimate  is  no  longer  tenable,  as  it  is 
generally  admitted  that  the  fungi  and  insects  are  not  to  be  considered  the  origin,  but 
the  result,  of  the  dry  rot.  It  has  been  suggested  that  its  action  depends  on  the  forma- 
tion of  a  compound  of  lignum,  or  pure  woody  fibre,  with  corrosive  sublimate,  which  re- 
sists decomposition  in  circumstances  where  pure  lignum  is  liable  to  decay.  But  pure 
lignum  possesses  no  tendency  to  combine  with  corrosive  sublimate.  The  action  of 
this  substance  is  in  reality  confined  to  the  albumen,  with  which  it  unites  to  form  an 
insoluble  compound,  not  susceptible  of  spontaneous  decomposition,  and,  therefore,  in- 
capable of  exciting  fermentation.  Vegetable  and  animal  matters,  the  most  prone  to 
decomposition,  are  completely  deprived  of  their  property  of  putrefaction  and  fermenta- 
tion by  the  contact  of  corrosive  sublimate.  It  is  on  this  account  advantageously  em- 
ployed as  a  means  of  preserving  animal  and  vegetable  substances.  Its  expensivenesg 
in  this  country  is  a  great  obstacle  to  its  extensive  employment  on  timber  used  for  build- 
ing purposes,  for  fences,  bridges,  &c.  There  is  scarcely  any  antisceptic  application 
so  effectual.  By  Mr.  Kyan's  process,  the  timber  to  be  impregnated,  is  sawed  up  into 
planks,  and  soaked  for  seven  or  eight  days  in  a  solution  containing  one  pound  of  cor- 
rosive sublimate  to  five  gallons  of  water.  The  impregnation  may  be  easily  effected  in 
an  open  tank  ;  though  the  best  way  is  to  impregnate  the  timber  by  placing  it  in  an 
air-tight  box,  from  which  the  air  has  been  exhausted  as  much  as  possible  by  a  pump. 
The  solution  then  enters  the  pores  of  wood  freely,  being  pressed  into  them  by  a  force 
equal  to  about  one  hundred  pounds  to  the  square  inch.  —  ParneW  s  Applied  Chemistry. 


354  APPENDIX. 

JBT3t "3J8AT 

TABLE  XIX. 


Table  showing  the  Heating  Power  of  different  kinds  of  Wood,  drawn 
by  MM.  Peterson  and  Schodler,  from  the  quantity  of  Oxygen  required 
to  burn  them. 

Names  of  Trees.  Oxygen  required  to  burn  them. 

Tila  Europea,  lime, 140-523 

Ulmus  suberosa,  elm, 139-408 

Pinus  abies,  fir, 138-377 

Pinus  larix,  larch, 138-082 

JEsculus  hippocastanum,  horse-chestnut, 138-002 

Buxus  sempervirens,  box, 137-315 

Acer  campestres,  maple,      136-960 

Pinus  sylvestris,  Scotch  fir, 136-931 

Pinus  pinea,  pitch  pine, 136-886 

Populus  nigra,  black  poplar, 136-628 

Pyrus  communis,  pear  tree, 135-881 

Juglans  regia,  walnut,      135-690 

Betula  alnus,  alder, 133-956 

Salix  fragilis,  willow, 133-951 

Quercus  robur,  oak, ,   .  133-472 

Pyrus  malus,  apple-tree, 133-340 

Fraxinus  excelsior,  ash, 133-251 

Betula  alba,  birch, 133.229 

Prunus  cerasus,  cherry-tree,      133-139 

Robinea  pseudacacia,  acacia, 132-543 

Fagus  sylvatica,  white  beach, 132-312 

Prunus  domestica,  plum, 132-088 

Fagus  sylvatica,  red  beach, 130-834 

Diospyros  ebenum,  ebony, 128-178 


APPENDIX. 


TABLE   XX. 

Difference  in  Weight  of  two  columns  of  Water,  each  one  foot  high,  at 
various  Temperatures, 


Difference  in 

temperature 

of  the  two 
columns  of 
water  in 
degrees  of 

Difference  in  weight  of  two  columns  of  water, 
contained  in  different  sized  pipes. 

Difference  of  a 
column  one  foot 
high. 

Fahrenheit's 

Scale. 

1  inch  dia.  2  inches  dia. 

3  inches  dia. 

4  inches  dia. 

per  square  inch. 

grs.  weight. 

grs.  weight. 

grs.  weight. 

grs.  weight. 

grs.  weight. 

2° 

1-5 

6-3 

14-3 

25-4 

2-028 

4 

3-1 

12-7 

28-8 

51-1 

4-068 

6 

4-7 

19-1 

43-3 

767 

6-108 

8 

6-4 

25-6 

57-9 

102-5 

8-160 

10 

8-0 

32-0 

72-3 

128-1 

10-200 

12 

9-6 

38-5 

87-0 

154-1 

12-264 

14 

11-2 

45-0 

101-7 

180-0 

14-328 

16 

12-8 

51-4 

116-3 

205-9 

16-392 

18 

14-4 

57-9 

131-0 

231-9 

18-456 

20 

16-1 

64-5 

145-7 

258-0 

20-532 

*#*  It  will  be  observed  in  the  above  table  that  the  amount  of  motive 
power  increases  with  the  size  of  the  pipe  j  for  instance,  the  power  is 
4  times  as  great  in  a  pipe  of  4  inches  diameter  as  in  one  of  2  inches. 
The  power,  however,  bears  exactly  the  same  relative  proportion  to  the 
resistance,  or  weight  of  water  to  be  put  in  motion  in  all  the  sizes  alike  j 
for,  although  the  motive  power  is  4  times  as  great  in  pipes  of  4  inches 
diameter,  as  in  pipes  of  2  inches,  the  former  contains  4  times  as  much 
water  as  the  other.  The  power  and  the  resistance,  therefore,  are  rela- 
tively the  same. 


INDEX  TO  THE  ILLUSTRATIONS. 


PART  I. 


SECTION    I. 

Fio.  PAGE. 

1  Elevations  of  hot-house  roofs, 35 

2  Difference  of  elevation  of  the  sun's  rays  at  Philadelphia  and  London,  .   .  36 

3  End  section  of  a  forcing  pit,     .   .   . 39 

4  Ground  plan  and  elevation  of  forcing  pit, 41 

5  End  section  of  a  stove, 42 

6  Polyprosopic  forcing  house, 43 

7  Cambridge  pit, 43 

8  Saunders'  pit, 48 

9  Curvilinear  cold  pit,  .   .   . 46 

10  Dung  bed  with  frame  for  forcing, 46 

1 1  Portable  glass  frame,     48 

12  Portable  plant  protector, 43 

13  Ground  plan  ofan  extensive  framing  ground, 51 

14  Range  of  graperies  at  Clifton  Park, 53 

15  Single-roofed  grapery, 55 

16  Span-roofed  house  on  the  same  scale, 55 

17  Single-roofed  curvilinear  grapery, 57 

18  Double-roofed  house  of  the  same  plan, 57 

19  Polyprosopic  grapery, 61 

20  Ground  plan  of  do., 61 

21  Ridge  and  furrow  roof, 65 

22  Range  of  small  houses, 69 

23  Ornamental  grapery, 71 

24  End  section  of  green-house, 76 

25  Perspective  view  of  span-roofed  green-house, 77 

26  Range  of  plant-houses, 78 

27  Ornamental  plant-house,       80 


SECTION    II. 

28  Roof  trellises, •  .  85 

29  Interior  trellises, 86 

30  Upright  trellises, 87 

31  Rooftrellises  and  open  border  planting, 87 

32  Interior  ground  plan  of  a  conservatory, 95 


ILLUSTRATIONS.  357 


PART    II. 

FIG.  PAGE. 

33  Williams'  furnace  for  prevention  of  smoke , 149 

34  Jeffreys' smoke-precipitating  furnace, 151 

35  Improved  arch  boiler, 179 

36  Common  boiler, 179 

36  A  Circular  boiler  and  pipes, 185 

37  Ground  plan  of  polmaise  heated  green-house,       197 

38  End  section  of  do., 198 

39  Longitudinal  section  of  do., 199 

40  Combination  of  hot  water  and  hot  air, 201 

41  Four  houses  heated  with  one  boiler, 204 

42  Boiler  and  supply  box, 205 

B   Supply  cistern, 205 

43  Tank  method  of  heating, 210 

44  Tank  of  galvanized  zinc, 214 

45  Wooden  tank  for  retention  of  heat, 216 

46  End  section  of  do., 216 

47  Plant  pits  heated  by  wooden  tanks, 227 

48  Arched  borders  heated  with  hot-water  pipes, 230 

49  Chambered  border  heated  with  tanks, 233 

50  Covered  hot  wall, 241 


PART  III. 

52  Method  of  ventilating  lean-to  houses  by  pulleys, 277 

53  End  section,  showing  the  apertures  for  ventilation  through  the  walls,  .  277 

54  End  section  of  span  roof,  showing  ventilation  at  top, 278 

55  Showing  the  ventilator  enlarged,      279 

56  Front  ventilation  by  rachet  wheel, 280 

57  Movement  of  the  atmosphere  from  the  floor  of  the  house, 289 

SB  Common  methods  of  ventilation .291 


TABLES. 


I.  Table  of  the  expansive  force  of  steam  in  pounds  per  square  inch,  for  tem- 
peratures above  212°  Fahrenheit, 335 

II.  Table  of  the  quantity  of  vapor  contained  in  atmospheric  air  at  different 
temperatures,  when  saturated, 336 

III.  Table  of  the  expansion  of  air  and  other  gases  by  heat,  when  perfectly 
free  from  vapor, 337 

IV.  Table  of  specific  gravity  and  expansion  of  water  at  different  temper- 
atures  338 

V.  Table  of  specific  heat,  specific  gravity,  and  expansion  by  heat  of  different 
bodies, 339 

VI.  Table  of  the  effects  of  heat, 340 

VII.  Table  of  the  quantity  of  water  contained  in  100  feet  of  pipe  of  different 
diameters,     341 

VIII.  Table  showing  the  effects  of  wind  in  cooling  glass, 341 

IX.  Experiments  on  the  cooling  effect  of  windows, 342 

X.  Weights  of  watery  vapor  in  one  cubic  foot  of  air,  at  dew  points  from  0°  to 
100°  Fahrenheit, 344 

XI.  Dalton's  table  of  the  force  of  vapor,  from  32°  to  80°, 345 

XII.  Table  for  ascertaining  dew  point  by  observations  on  the  wet  and  dry 
bulb  thermometer, 346 

XIII.  Table  of  the  analysis  of  confined  air, 348 

XIV.  Constitution  of  the  atmosphere  ;  consumption  of  oxygen,  and  formation 
of  carbonic  acid, -. 349 

XV.  Table  of  mean  temperatures  of  the  hottest  and  coldest  months,    .   .  350 

XVI.  Mean  temperature  of  the  earth  and  of  the  atmosphere, 351 

XVII.  Specific  gravity  of  different  kinds  of  timber, 352 

XVIII.  Solutions  for  the  impregnation  of  wood  which  is  exposed  to  the  at- 
mosphere, for  the  purpose  of  preserving  it  from  decay, 353 

XIX.  Heating  power  of  different  lunds  of  wood,  drawn  from  the  quantity 
of  oxygen  required  to  burn  them, 354 

XX.  Difference  of  weight  of  two  columns  of  water,  each  one  foot  high,  at 
various  temperatures, 455 


INDEX. 
PART  I. -CONSTRUCTION. 

SECTION    I. 

SITUATION. 

Site  and  position. — What  is  to  be  understood  by  site  and  position.  —  Cir- 
cumstances to  affect  the  position  of  a  hot-house. — Avoid  bare,  elevated  spots.  — 
Reasons  for  so  doing. — For  shelter.  —  For  beauty  and  effect, 13 

Terraces. — Their  origin,  and  use  round  horticultural  buildings.  —  The  un- 
sightliness  of  turf  terraces.  —  Architectural  terraces.  —  Description  of  a  terrace 
at  a  gentleman's  residence.  —  Effect  of  trees.  —  Effect  without  trees.  —  Choice 
of  position  decided  by  other  circumstances, 15 

Aspect.  —  Best  aspect  for  lean-to  houses.  —  Reasons  for  choosing  a  south- 
eastern aspect.  —  Aspect  for  span-roofed  houses.  —  The  aspect  of  conserva- 
tories. —  Unsuitable  conservatories, 20 

SECTION    II. 
DESIGN. 

General  principles.  —  Object  of  hot-houses.  —  Agents  of  vegetative  growth.  — 
Reasons  wnybad  structures  are  so  generally  erected  in  this  country.  —  Mansion 
architects.  —  Their  incapacity  for  erecting  horticultural  buildings.  —  Fitness  for 
the  end  in  view.  —  Solid,  opaque  conservatories.  —  Conservatory  at  Brookline. 
—  Absurdity  of  spending  large  sums  on  conservatories.  —  Observations  of  an 
architect.  —  Massive  conservatories, 25 

Light  a  primary  object.  —  Wonderful  effects  of  light  on  vegetables.  — Theory 
of  the  transmission  of  light. — Rays  of  light  reflected  from  transparent  sur- 
faces. —  Action  of  light  upon  plants.  —  Effects  of  different  rays.  —  Light  which 
has  permeated  yellow  media.  — Light  which  has  permeated  red  media.  —  Light 
which  has  permeated  blue  media.  —  Difficulty  of  obtaining  pure  colors.  — 
Amount  of  assimilation  and  perspiration  in  plants.  —  Necessity  ot  making  plant- 
houses  transparent  on  all  sides, 29 

Slope  of  hot-house  roofs.  —  Much  depends  on  the  angle  of  elevation.  — Prin- 
ciples to  guide  the  inclination  of  hot-house  roofs.  —  Elevations  of  roofs  in 
England.  —  Figure  representing  different  elevations.  —  Figure  showing  the  dif- 
ference of  latitude  between  London  and  Philadelphia.  —  Application  of  these 


360 


INDEX. 


principles.  — Error  committed  in  laying  hot-house  roofs  too  flat.  —  Table  show- 
ing the  number  of  rays  reflected  at  different  angles.  —  Circumstances  on  which 
the  slope  of  roofs  depends, 34 


SECTION    III. 
STRUCTURES    ADAPTED    TO     PARTICULAR      PURPOSES. 

Forcing-houses,  culinary-houses,  &c.  —  Purposes  of  their  erection.  —  Section 
of  a  forcing-pit  figured  and  described.  — Large  forcing-pit  figured  and  described. 
—  Dimensions  of  winter  forcing-houses.  —  Skill  required  in  the  forcing  of  fruit 
in  winter.  —  Polyprosopic  forcing-houses  figured  and  described. — Advantages 
of  pplyprosopic  roofs, 39 

Pits.  —The  Cambridge  pit.  —  Saunders'  forcing-pit  figured  and  described.  — 
Curvilinear  roofed  cold  pits.  — Dung  beds.  —  Temporary  frames.  — Plant  pro- 
tectors.—  Figures  and  descriptions  of  them, 43 

Framing  ground.  —  Its  purposes.  —  General  condition  of  this  department.  — 
Appropriate  site  for  it.  —  Ground  plan  and  disposition  of  framing  ground,  .  49 

Orangeries,  graperies,  &c.  —  Latitude  given  in  their  construction.  —  Repre- 
sentation of  a  range  of  cold-houses  at  Clifton  Park.  —  Size  of  cold-houses.  — 
Figures  of  lean-to  and  span-roofed  houses. — Figures  of  double  and  single- 
roofed  curvilinear  houses, 54 

Objections  raised  against  curvilinear  houses  in  England.  —  Properties  pos- 
sessed by  curvilinear  houses.  —  Reflection  and  refraction  of  light  by  them.  — 
Their  adaptability  for  grape-growing.  —  Gable  ends.  —  Objections  to  them,  .  58 

Polyprosopic  houses.  —  Figures  and  descriptions  of  do.  —  Double-roofed 
houses  of  this  kind.  —  Cold  vineries.  —  Disadvantages  attending  them.  — 
Front  wall  of  hot-houses.  —  The  height  of  do.  —  Objections  to  upright  fronts.  — 

Parapet  walls, 60 

_  Ridge  and  furrow-roofed  houses.  —  Figure  and  description  of  a  house  of  this 
kind.  —  Directions  for  building  ridges  and  furrows.  —  Glazing  of  do.  —  Advan- 
tages of  do. —  Principle  of  their  construction, 64 

Cold  vineries.  —  Range  of  small  booses  figured  and  described.  —  Advantages 
of  small  houses  over  large  ones, 67 

Green-houses,  conservatories,  &c.  —  Distinction  between  green-houses  and 
conservatories.  —  Amalgamation  of  the  two  together.  —  Appropriation  of  green- 
houses in  summer.  —  Span-roofed  green-houses  preferable  to  single-roofed  ones. 
— Beauty  of  well-grown  plants.  —  Impossibility  of  growing  plants  well  in  opaque 
houses.  —  Proportions  of  a  green-house, " 73 

Plan  of  green-house,  and  description.  —  Prospective  view  of  green-house.  — 
Range  of  green-houses.  —  Height  of  plant-houses.  —Errors  in  making  them  too 
high.  —  Conservatory  at  Regent's  Park  Botanic  Garden.  —  Principles  of  design 
and  taste  displayed.  —  Advantages  of  low-roofed  plant-houses, 76 


SECTION    IV. 

INTERIOR      ARRANGEMENTS. 

Arrangements  for  forcing-houses,  culinary-houses,  &c.  —  Trellises  and  meth- 
ods of  fixing  trellises.  —  Roof  trellises.  —  Centre  trellises.  —  Cross  trellises. 
—  Trellises  for  double  houses, 84 

Interior  of  green-houses.  —  Slope  of  sfreen-house  stages.  — Green-houses  for 
promiscuous  plants.  —  Width  and  height  of  green-house  shelves.  —  Stages  for 
small  plants,  &c., 87 

Conservatories,  Orangeries,  &e.  —  Houses  for  growing  large  plants.  — Con- 
servatory beds. —  Level  of  do.  —  Objections  to  the  general  form  of  conserva- 
tory beds.  —  Irregular  method  of  laying  out  the  interior  of  conservatories.  — 
This  method  illustrated  in  the  conservatory  at  the  Royal  Botanic  Garden,  Re- 
gent's Park.  —  Ground  plan  of  a  conservatory  laid  out  in  the  irregular  style.  — 
Advantages  resulting  from  this  method, 89 


INDEX.  361 

SECTION    V. 

MATERIALS      OF      CONSTRUCTION. 

Workmanship.  —  Bad  foundations,  &c.  —  Temporary  nature  of  horticultural 
erections.  —  Consequence  of  bad  constructed  houses.  —  Superior  workmanship. 

—  Economy  of  building  substantial  houses, 99 

Materials  of  const  rueaon.  —  Most  suitable  materials  for  building  hot-houses. 

—  Metallic   houses  —  Superior   to  wood. — Opposition  to   iron   hot-houses. — 
Objections  raised.  —  Objections   answered.  —  Expansibility    of   copper  —  Of 
iron. — Power  of  metals  to  conduct   heat.  —  Electricity  an  objection.  —  Cost 
of  iron  hot-houses.  —  Mr.  Ressor's  iron  vinery.  —  Horticultural  structures  in 
Europe  of  iron.  —  Transportability  of  materials,  &c., 101 

SECTION    VI. 

GLASS. 

The  physical  properties  of  transparent  bodies.  —  Glass  of  the  palm-house  at 
Kew.  —  Report  of  Mr.  Hunt,  from  Silliman's  Journal  of  Science.  —  Calorific 
influence  of  the  glass  chosen.  —  Action  of  the  non-luminous  rays  of  light.  — 
Green  glass  of  Melloni, 106 

Evils  consequent  on  -employing  bad  glass  in  hot-houses.  —  Knotted  and 
wavy  glass.  —  Its  effects.  —  Resources  against  bad  glass.  —  Painting  and  shad- 
ing the  glass.  —  Inconveniencies  attending  both  these  methods.  —  Utility  of 
using  good  glass. — Propriety  of  manufacturers  of  glass  making  good  mate- 
rial,   109 

Glazing.  —  Siz«e  of  laps.  — Glazing  roof-sashes,.  —Objectionable  nature  of 
broad  laps.  —  The  most  approved  method  of  making  laps.  —  Curvilinear  glaz- 
ing. —  Reversed  curvilinear  glazing.  —  Puttying  the  laps.  —  Glaring  ridge  aod 
furrow  roofs.  —  Anomalous  surfaces, 110 

Color  of  walls.  —  Considerations  in  favor  of  a  dark  color. — Influence  of 
reflected  light  on  dark  walls.  —  Retention  of  heat  by  dark-colored  walls.  — 
Color  of  the  rafters.  —  Painting  of  the  wood-work  of  the  house  with  an  anti- 
corrosive  solution, 113 


SECTION  VII. 
FORMATION   OF  GARDENS. 

Form  of  the  garden  and  disposition  of  the  ground.  —  Considerations  neces- 
sary for  fixing  on  the  site.  —  Walks.  —  Entrance-walk.  —  Formation  of  walks. 
—  Different  kinds  of  walks.  —  The  durability  and  comfort  of  walks.—  Materials 
for  the  surface  of  walks.  —  Form  of  the  surface.  —  Edges  of  walks,  .  .  .  .116 

Borders  and  compartments.  —  Width  and  size  of  do.  —  General  rule  for  lay- 
ing down  borders.  —  Size  and  number  of  compartments.  —  Bad  effects  of  small 
walks,  . 119 

Walls  — their  'ise. —  Forms  of  walls.  —  Their  height.  —Gardens  of  Mr. 
Cushing,  at  Watertown.  —  Hot  and  flued  walls.  —  Wooden  fences.  — Com- 
parative economy  dt  walls  and  fences, 121 


362  INDEX. 


PART  II. -HEATING. 

SECTION    I. 

PRINCIPLES      OF      COMBUSTION. 

The  nature  and  properties  of  fuel.  —  Considerations  on  the  subject.  —  Char- 
acteristics in  the  use  of  coals  pointed  out.  —  Result  of  the  application  of  heat 
to  coal.  —  Disengagement  of  gas.  —  Gases  endowed  with  the  power  of  giving  out 
heat.  —  Combustibility.  — What  is  combustion.  —  The  heating  power  of  gas,  125 

Inquiry  into  the  combustion  of  coal  gas.  —  Doctrine  of  equivalents.  —  Ob- 
servations of  Mr.  Parks.  —  Disproportion  between  the  volumes  of  the  constituent 
parts.  — Different  kinds  of  gases  generated.  —Bulk  of  gases  represented  by 
figures 132 

Atmospheric  air.  —  Its  constituents  represented  by  diagrams.  —  The  com- 
ponent parts  of  different  gases  represented  by  diagrams.  —  Union  of  the  con- 
stituents. —  Chemical  law  in  relation  to  these  gases.  —  Carbon  vapor,  .  .  .  137 

Formation  of  carburetted  hydrogen.  —  Excess  and  deficiency  of  heat-producing 
ingredients.  —  The  union  of  oxygen  with  smoke.  —  Quantity  of  air  required  to 
supply  the  requisite  quantity  of  oxygen.  —  How  ordinary  furnaces  are  incapable 
of  consuming  coal  perfectly.  — The  complete  combustion  of  bodies,  ....  145 

Argand  lamp.  —  Williams'  smoke-preventing  furnace  figured  and  described. 

—  Jeffries' smoke-precipitating  furnace  figured   and  described.  —  Their  value 
considered.  —  Application  of  these  inventions  in  Europe.  — Methods  of  burning 
smoke, 148 

Construction  of  furnaces.  —  For  heating  large  boilers.  —  For  making  the 
fuel  last  a  long  time.  —  Considerations  necessary  to  be  noticed  in  building  the 
furnace.  —  The  kind  of  fuel  to  be  consumed.  —  Size  and  width  of  bars.  — 
Table  for  ascertaining  the  area  of  furnaces, 153 

SECTION    II. 

PRINCIPLES      OF      HEATING     HOT-HOUSES. 

Effects  of  artificial  heat.  —  Changes  produced  by  it.  —  Animal  and  vegetable 
matter  decomposed  by  it.  —  Hydrogen  eliminated  by  the  decomposition  of 
water.  —  Experiments  on  the  effects  of  heated  air.  —  Heat  from  brick  flues.  — 
Iron  radiators  more  injurious  than  others, 156 

Laws  of  heat.  —  Radiation  and  conduction.  —  Combined  effects  of  radiation. 

—  Proportion  they  bear  to  each  other.  —  Table  showing  the  velocities  of  cooling 
at  different  temperatures.  —  Experiments  on  cooling  of  iron  pipes.  —  Specific 
heat  of  air  and  water.  —  Horticultural  structures  different  from  opaque  build- 
ings.—  Causes  of  loss  of  heat, 158 

Table  showing  the  quantity  required  to  heat  given  volumes  of  air.  —  The 
effects  of  glass  windows  ascertained.  —  Experiments  on  glass  surfaces.  —  Table 
showing  the  results.  —  Specific  heat  of  air  and  water.  —  Application  to  hot- 
house buildings, 164 

SECTION    III. 
HEATING     BY     HOT     WATER,     HOT-AIR,  AND     STEAM. 

Practice  of  heating  by  hot  water.  —  Its  merits  considered.  —  Temperature 
of  hot- water  pipes.  —  Weight  of  steam.  —  Calculations  showing  the  superiority 
of  hot-water  pipes. — Permanancy  of  heat  by  hot  water, 167 


INDEX.  363 


Comparison  of  hot  air  with  hot  water,  as  a  method  of  heating  horticultural 
buildings.  —  Air  a  bad  conductor.  —  Evaporating  pans  for  supplying  moisture. 

—  Considered  in  respect  to  motion  in  the  atmosphere  —  in  respect  to  perma- 
nency of  heating  power.  —  Water  a  better  conductor.  —  Experiments  on  air  and 
water  as  modes  of  conducting  heat, 171 

SECTION    IV. 

HOT-WATER      BOILERS     AND     PIPES. 

Size  of  boilers,  and  surfaces  necessary  to  be  exposed  to  the  fire.  —  Adapta- 
tion of  the  boiler  to  the  apparatus.  —  Of  the  boiler  and  the  quantity  of  water 
contained.  —  The  repulsion  of  heat  by  the  metal  of  the  boiler.  —  Table  showing 
the  proportion  the  surface  exposed  to  the  fire  must  bear  to  the  quantity  of  pipe,  176 

Causes  tending  to  modify  the  proportions  to  be  adopted.  —  Figures  of  boilers. 

—  Estimated  action  of  the  fire  upon  the  boilers.  —  Material  for  boilers,  .    .  179 
Size  and  arrangement  of  hot-water  pipes  most  suitable  for  the  purposes  of 

heating.  —  Unequal  rate  of  cooling  in  the  various  sized  pipes.  —  The  ordinary 
methods  of  arranging  hot-water  apparatus.  — Advantage  of  taking  the  flue 
through  the  house.  —  Laying  down  hot-water  pipes. — Expansion  of  pipes 
when  heated.  —  Supply  cisterns, 181 

Impediments  to  circulation.  —  Causes  of  circulation.  —  Amount  of  motive- 
power.  —  Table  showing  the  weight  of  water  at  different  temperatures.  — 
Trifling  cause  renders  an  apparatus  inefficient.  —  Methods  of  increasing  the 
motive-power. — The  rapidity  of  circulation  in  proportion  to  the  motive- 
power 184 

Level  of  pipes.  —  Errors  committed  in  the  level  of  pipes.  —  Circulation  takes 
place  first  at  the  boiler.  —  Methods  of  making  water  circulate  in  pipes  below 
the  level  of  the  boiler, 188 

Accumulation  of  air  in  pipes.  —  Provision  necessary  for  the  escape  of  air.  — 
Want  of  attention  to  this  the  cause  of  failures.  —  The  size  of  air  vents.  —  Diffi- 
culty of  finding  the  proper  place  to  place  the  air  vents, 190 

SECTION    V. 

VARIOUS  METHODS  OF  HEATING  DESCRIBED. 

Expense  attending  the  ordinary  methods  of  heating.  —  Polmaise  method  of 
heating.  —  Its  adoption  in  houses  in  this  country.  —  Its  origin.  —  Means  em- 
ployed to  promote  it  in  England.  —  Description  and  figures  of  this  method,  .  192 

A  method  of  combining  hot  air  and  hot  water  together.  —  Figured  and  de- 
scribed. —  Advantages  of  this  method  in  the  generation  of  heat  and  saving  of 
fuel, 200 

Compound  method  of  heating.  —  Seven  ranges  of  houses  heated  by  this 
method.  —  Figure  representing  four  houses  heated  by  this  plan.  —  Figure  of 
boiler  and  box.  —  Of  supply  cisterns.  —  Advantages  of  this  mode  of  heating.  — 
Saving  of  fuel  by  it.  —  Simplicity  of  working, 203 

Tank  methods  of  heating.  —  Methods  figured  and  described.  —  Wooden  and 
metallic  tanks.  —  The  merits  and  properties  of  each.  — Utility  and  simplicity 
of  do., .  .  .211 

Fertilization  of  the  atmosphere  by  tanks.  —  Dissolving  volatile  gases  in  tanks. 
Their  use  in  English  nurseries  for  growing  young  stock.  —  Their  adaptation  to 
amateurs,  in  small  pits, 223 

Representation  of  plant  pits  and  description.  —  Uses  of  these  pits.  —  Protec- 
tion of  plants  during  winter  in  them, 226 

Chambered  vine  borders.  —  Argument  in  favor  of  them.  —  Their  utility 
under  certain  circumstances.  —  Figure  and  description  of  a  chambered  border. 

—  Evidence  in  favor  of  them, 228 

Cheap  method  of  forming  a  chambered  vine  border.  —  Comparison  of  cost  of 

it  with  manure.  —  Economy  of  their  adoption.  — Method  of  managing  them.  — 
Coverings  of  borders,  234 

31* 


364  INDEX. 


Construction  of  hot  walls.  —  Figure  and  description  of  hot  wall.  —  Various 
methods  of  building  hot  walls.  —  Trial  of  hot  walls,  covered  and  uncovered.  — 
Foreign  grapes  may  be  grown  on  hot  walls.  — Grapes  produced  on  hot  walls  in 
England, 2iO 

New  method  of  propelling  heated  air  by  means  of  machinery  —  described  by 
Mr.  Marhock  in  Gardeners'  Journal.  —  The  air  propelled  by  means  of  a  fan,  246 


PART  III. -VENTILATION. 

SECTION    I. 

PRINCIPLES    OF    VENTILATION. 

Attention  required  from  gardeners,  &c.  —Its  practical  importance.  — Power 
of  plants  to  withstand  the^changes  of  climate.  —  Power  of  vitality  possessed 
by  seeds.  —  Power  of  plants  to  bear  high  temperatures. — Of  bearing  delete- 
rious gases.  —  Effect  of  winter-forcing  on  the  odor  of  flowers  —  and  on  the 
flavor  of  fruits, 248 

Whether  vegetation  purifies  the  air.  —  Opinions  of  Priestley  —  of  Dr.  Dau- 
beny,  of  Oxford  —  of  Dr.  Lindley,  of  London.  —  Natural  adjustment  of  the 
atmospherical  elements.  —  Atmosphere  of  cities. —  Benefits  of  large  trees  in 
the  streets.  —  New  Haven,  the  effect  of  trees  in  it, 252 

Power  of  plants  to  absorb  carbonic  acid.  —  Gottingen  springs.  —  Property  of 
charcoal  for  absorbing  gases.  —  Table  of  gases  and  the  quantities  absorbed  by 
charcoal, 254 

Power  of  plants  to  withstand  the  vicissitudes  of  temperature.  —  Theories  of 
physiologists.  —  Dalton's  chemical  philosophy.  —  His  theory  of  the  relations  of 
the  atmosphere  to  heat.  —  The  properties  possessed  by  caloric, 256 

SECTION    II. 

EFFECTS     OF     VENTILATION. 

Effects  of  admitting  cold  air  into  a  hot-house. — Moisture  carried  away. — 
Necessity  of  keeping  the  floors  damp. — Plants  unlike  animals  in  respect  to 
ventilation.  —  Ventilation  not  necessary  as  regards  respiration.  —  Air-tight 
glass  cases  for  plants, 262 

Knight's  experiments  on  grape  vines.  —  The  philosophy  of  this  system. — 
Evaporation  of  moisture  on  the  glass.  —  Contaminating  gases  in  the  atmos- 
phere.—  Experiments  of  Drs.  Turner  and  Christison, 264 

The  abstraction  of  moisture  in  proportion  to  the  rapidity  of  the  motion  of  the 
air.  —  Methods  of  counteracting  this  loss. — Thermometric  changes  not  sat- 
isfactory rules  for  the  admission  of  air,  266 

Quantity  of  moisture  contained  in  the  air.  —  Its  capacity  for  moisture. — 
Estimated  quantity  of  air  escaped.  — Estimated  quantity  of  moisture  escaping 
in  the  air.  —  Lofty  plant-houses.  —  Difficulty  of  managing  the  atmosphere  in 
them, 269 

SE  CTION    III. 

METHODS      OF      VENTILATION. 

Improvements  of  the  present  methods  of  ventilation.  —  Plans  adopted  to 
modify  the  influence  of  draughts. —  Motion  in  the  atmosphere.  —  Machinery 
employed  for  this  purpose.  —  Detection  of  currents  by  a  common  candle. — 
Propriety  of  a  rapid  motion  disputed, 273 


INDEX.  365 


Difficulty  of  managing  the  atmosphere  in  large,  dome-shaped  houses. — 
Covering  necessary.  —  To  equalize  the  temperature.  —  The  natural  law  of 
equality  ineffectual.  —  The  slightest  cause  disturbs  the  equilibrium  of  the  air. 
—  The  extreme  sensibility  of  the  air.  —  Irregularity  of  its  temperature  in  hot- 
houses. —  The  causes  of  this  irregularity.  —  Experiments  of  Gay  Lussac  — 
of  Rudberg, 275 

A  new  method  of  ventilation.  —  Adapted  to  lean-to  houses.  —  Figured  and  de- 
scribed.—  Facility  with  which  this  method  may  be  wrought, 277 

Method  of  ventilating  span-roofed  houses.  — Adopted  in  the  new  hot-houses 
at  Frogmore.  —  Figures  and  description  of  this  method, 279 

Methods  of  airing  by  the  rachet  wheels.  — By  springs.  —  Superiority  of  the 
former.  —  Necessity  of  having  the  machinery  for  ventilation  properly  erected.  — 
Its  liability  to  get  out  of  repair.  —  Method  applauded  without  merit.  —  Neces- 
sity of  guarding  against  the  applauded  inventions  of  any  one, 280 


SECTION    IV. 

MANAGEMENT      OF      THE      ATMOSPHERE. 

Atmospheric  motion.  — Admitting  large  quantities  of  cold  air.  —  The  results 
of  this  method.  —  Questions  arising  out  of  these  considerations.  —  The  quantity 
of  air  to  be  admitted. — Motion  affected  by  various  circumstances.  —  The 
atmosphere  of  a  hot-house  influenced  by  the  glazing  of  the  sashes.  —  Effect 
produced  by  radiation.  —  Growth  of  plants  in  Wardian  cases.  —  Deterioration 
of  air  by  flues,  &c.,  284 

Method  of  airing  without  opening  the  sashes.  —  Figured  and  described.  — 
This  method  recommended  for  houses  during  cold  weather  in  winter,  .  .  .  288 

Common  method  of  ventilating  figured  and  described.  —  Evils  resulting  from 
this  method. — Action  in  cold  weather, 290 

Contrivance  for  admitting  warmed  air  into  the  house  over  the  heating  appa- 
ratus. — By  a  serpentine  conductor.  —  Size  of  the  tubes  necessary.  —  Radiation 
of  heat  from  the  surface  of  the  flue.  —  The  effects  of  the  external  air  neutral- 
ized by  this  method, 292 

The  system  of  ventilation.  —  Its  object  being  to  prevent  a  stagnation  in  the 
atmosphere.  —  Evils  of  this  method  shown  and  explained.  —  Mechanical  and 
chemical  effects  of  ventilation, 293 


SECTION    V. 

CHEMICAL     COMBINATIONS     IN     THE     ATMOSPHERE 
OF      H  OT-HOUSE  S. 

Nourishment  plants  ought  to  receive  from  the  atmosphere.  —  How  to  receive 
it.  —  Starch  and  sugar.  —  Their  different  properties.  —  Questions  arising  from 
considerations  of  their  properties.  —  Experiments  on  the  atmosphere. — The 
importance  of  oxygen  to  vegetable  life, 296 

Atmosphere  from  fermenting  manure.  —  Quality  of  heat  generated  by  it.  — 
Impregnation  of  the  atmosphere  with  ammonia.  —  Experiments  on  the  atmos- 
phere of  a  green-house  with  ammoniacal  gas, .  .299 

Composition  of  ammonia.  — Excess  of  ammonia.  —  Its  suffocating  influence. 
—  Illustrations  of  its  effects.  —  Fumigation  of  plant-houses  and  pits  with 
ammonia. — The  cause  of  luxuriance  in  plants. — Produced  largely  from  fer- 
menting manure,  &c.,  300 

What  guides  we  have  to  ascertain  the  various  changes  in  the  atmospheric 
elements.  —  Disagreeable  smell  on  entering  a  hot-house.  —  The  cause,  and  how 
to  remedy  it.  —  The  important  part  played  by  oxygen  in  this  process.  —  Pro- 
portion of  oxygen  necessary  to  vegetables.  —  Amount  contained  in  atmospheric 
air  and  water.  —  Affinity  of  its  elements, 303 


366  INDEX. 

Beautiful  adaptation  of  the  atmosphere  to  plants  and  animals.  —  Effect  of 
pure  oxygen.  —  Property  of  watery  vapor  in  vegetable  economy.  —  Subtlety  of 
the  air.  —  Necessity  of  maintaining  an  adequate  supply  of  aqueous  vapor  in  the 
atmosphere.  —  Instruments  for  guiding  us  m  regulating  the  atmosphere.  —  In- 
struments much  wanted  for  measuring  the  respective  quantities  of  the  gaseous 
elements, 305 


SECTION    VI. 

PROTECTION      OF      PLANT-HOUSES      DURING      COLD 
NIGHTS. 

Advantages  of  protecting  bodies.  — Conditions  of  the  plants  at  low  temper- 
atures.—  Light  coverings  otherwise  useful.  —  Experiments  on  the  cooling 
effects  of  wind.  —  Materials  for  protecting  glazed  structures.  —  Methods  of 
protection,  309 

Slight  covering  that  is  required  to  protect  plants  from  frost.  —  Experiments 
of  Dr.  Wells  on  coverings.  —  Method  of  covering.  —  Distance  to  keep  the  cov- 
ering from  the  object  protected, •  ...  313 

Effects  of  vertical  coverings.  —  Horizontal  coverings.  —  Coverings  of  straw, 
etc.  — Protection  afforded  by  walls.  — Protection  of  snow.  —  Warmth  afforded 
by  the  soil  to  trees  in  winter, 31T 


SECTION    VII. 

GENERAL      REMARKS      ON      THE      MANAGEMENT      OF 
THE      ATMOSPHERE      OF      HOT-HOUSES. 

Adjustment  of  the  artificial  to  the  natural  atmosphere.  —  Observations  of 
Knight.  —  Rest  necessary  to  plants  during  night.  —  Cause  of  the  imperfect 
maturation  of  fruit-tree  blossoms.  —  High  night  temperatures  exhaust  the  ex- 
citability of  the  trees.  — Plants  continue  longer  in  bloom  in  low  night  temper- 
atures. —  Admission  of  external  air  during  day.  —  Difference  of  climate  be- 
tween this  country  and  England, 320 

Rules  to  be  observed  by  the  gardener  in  charge  of  hot-houses.  —  Dutch  meth- 
od of  forcing.  —  Excessive  moisture  —  its  effects.  —  Necessity  for  periods  of 
rest  to  plants.  —  Changing  the  period  of  fructification, 325 


SECTION    VIII. 
VENTILATION     WITH     FANS. 

Construction  of  ventilating  fans.  —  Methods  of  using  them.  —  Their  adapta- 
tion to  horticultural  purposes.  —  Different  kinds  of  fans.  —  Objects  to  be  ef- 
fected by  them.  —  Requisites  to  the  use  of  fans.  —  Windmill  ventilators.  — 
Their  employment  in  horticultural  buildings.  —  Pump  ventilators.  —  Ventila- 
tion by  means  of  chimney  shafts,  &c 329 


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